[REEF-1755] Clean up for IMRU test validation messages

JIRA:
  [REEF-1755](https://issues.apache.org/jira/browse/REEF-1755)

Pull request:
  This closes #1275
diff --git a/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/IMRUBrodcastReduceTestBase.cs b/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/IMRUBrodcastReduceTestBase.cs
index 5e98373..4555d7b 100644
--- a/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/IMRUBrodcastReduceTestBase.cs
+++ b/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/IMRUBrodcastReduceTestBase.cs
@@ -56,6 +56,7 @@
         protected const string FailedTaskMessage = IMRUDriver<int[], int[], int[], int[]>.FailedTaskMessage;
         protected const string FailedEvaluatorMessage = IMRUDriver<int[], int[], int[], int[]>.FailedEvaluatorMessage;
         protected const string DoneActionMessage = IMRUDriver<int[], int[], int[], int[]>.DoneActionPrefix;
+        protected const string FailedActionMessage = IMRUDriver<int[], int[], int[], int[]>.FailActionPrefix;
 
         /// <summary>
         /// Abstract method for subclass to override it to provide configurations for driver handlers 
diff --git a/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/TestExceptionInResultHandlerDispose.cs b/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/TestExceptionInResultHandlerDispose.cs
index 3ee5a45..945bc06 100644
--- a/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/TestExceptionInResultHandlerDispose.cs
+++ b/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/TestExceptionInResultHandlerDispose.cs
@@ -48,7 +48,7 @@
             string testFolder = DefaultRuntimeFolder + TestId;
             TestBroadCastAndReduce(false, numTasks, chunkSize, dims, iterations, mapperMemory, updateTaskMemory, numberOfRetryInRecovery, testFolder);
             string[] lines = ReadLogFile(DriverStdout, "driver", testFolder, 120);
-            var completedTaskCount = GetMessageCount(lines, "Received ICompletedTask");
+            var completedTaskCount = GetMessageCount(lines, CompletedTaskMessage);
             var failedEvaluatorCount = GetMessageCount(lines, FailedEvaluatorMessage);
             var failedTaskCount = GetMessageCount(lines, FailedTaskMessage);
             var jobSuccess = GetMessageCount(lines, DoneActionMessage);
diff --git a/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/TestFailMapperEvaluatorsOnInit.cs b/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/TestFailMapperEvaluatorsOnInit.cs
index 1246b67..0227282 100644
--- a/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/TestFailMapperEvaluatorsOnInit.cs
+++ b/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/TestFailMapperEvaluatorsOnInit.cs
@@ -53,7 +53,7 @@
                 NumberOfRetry,
                 testFolder);
             string[] lines = ReadLogFile(DriverStdout, "driver", testFolder, 360);
-            var completedTaskCount = GetMessageCount(lines, "Received ICompletedTask");
+            var completedTaskCount = GetMessageCount(lines, CompletedTaskMessage);
             var failedEvaluatorCount = GetMessageCount(lines, FailedEvaluatorMessage);
             var failedTaskCount = GetMessageCount(lines, FailedTaskMessage);
             var jobSuccess = GetMessageCount(lines, DoneActionMessage);
diff --git a/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/TestFailMapperEvaluatorsWithFailedResultHandlerOnDispose.cs b/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/TestFailMapperEvaluatorsWithFailedResultHandlerOnDispose.cs
index 9728973..10deef6 100644
--- a/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/TestFailMapperEvaluatorsWithFailedResultHandlerOnDispose.cs
+++ b/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/TestFailMapperEvaluatorsWithFailedResultHandlerOnDispose.cs
@@ -57,8 +57,8 @@
             // As the driver will shut down as soon as all tasks are in final state. The task state is final either by 
             // ICompletedTask or IFailedEvaluator. But MessageLogger may not be able to receive the last event 
             // before driver shut down. 
-            var failedEvaluatorCount = GetMessageCount(lines, "Received IFailedEvaluator");
-            var completedTaskCount = GetMessageCount(lines, "Received ICompletedTask");
+            var failedEvaluatorCount = GetMessageCount(lines, FailedEvaluatorMessage);
+            var completedTaskCount = GetMessageCount(lines, CompletedTaskMessage);
 
             var failedTaskCount = GetMessageCount(lines, FailedTaskMessage);
             var jobSuccess = GetMessageCount(lines, DoneActionMessage);
diff --git a/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/TestFailMapperTasks.cs b/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/TestFailMapperTasks.cs
index 41c6b77..6336c02 100644
--- a/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/TestFailMapperTasks.cs
+++ b/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/TestFailMapperTasks.cs
@@ -54,11 +54,11 @@
                 NumberOfRetry,
                 testFolder);
             string[] lines = ReadLogFile(DriverStdout, "driver", testFolder, 240);
-            var completedTaskCount = GetMessageCount(lines, "Received ICompletedTask");
+            var completedTaskCount = GetMessageCount(lines, CompletedTaskMessage);
             var runningTaskCount = GetMessageCount(lines, RunningTaskMessage);
             var failedEvaluatorCount = GetMessageCount(lines, FailedEvaluatorMessage);
             var failedTaskCount = GetMessageCount(lines, FailedTaskMessage);
-            var jobFailure = GetMessageCount(lines, IMRUDriver<int[], int[], int[], int[]>.FailActionPrefix);
+            var jobFailure = GetMessageCount(lines, FailedActionMessage);
 
             // each task should fail or complete
             // there should be no failed evaluators
diff --git a/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/TestFailMapperTasksOnDispose.cs b/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/TestFailMapperTasksOnDispose.cs
index cf897fb..798a970 100644
--- a/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/TestFailMapperTasksOnDispose.cs
+++ b/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/TestFailMapperTasksOnDispose.cs
@@ -53,7 +53,7 @@
                 NumberOfRetry,
                 testFolder);
             string[] lines = ReadLogFile(DriverStdout, "driver", testFolder, 360);
-            var completedTaskCount = GetMessageCount(lines, "Received ICompletedTask");
+            var completedTaskCount = GetMessageCount(lines, CompletedTaskMessage);
             var failedEvaluatorCount = GetMessageCount(lines, FailedEvaluatorMessage);
             var failedTaskCount = GetMessageCount(lines, FailedTaskMessage);
             var jobSuccess = GetMessageCount(lines, DoneActionMessage);
diff --git a/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/TestFailMapperTasksOnInit.cs b/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/TestFailMapperTasksOnInit.cs
index ca20a6c..f629c56 100644
--- a/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/TestFailMapperTasksOnInit.cs
+++ b/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/TestFailMapperTasksOnInit.cs
@@ -53,7 +53,7 @@
                 NumberOfRetry,
                 testFolder);
             string[] lines = ReadLogFile(DriverStdout, "driver", testFolder, 240);
-            var completedTaskCount = GetMessageCount(lines, "Received ICompletedTask");
+            var completedTaskCount = GetMessageCount(lines, CompletedTaskMessage);
             var failedEvaluatorCount = GetMessageCount(lines, FailedEvaluatorMessage);
             var failedTaskCount = GetMessageCount(lines, FailedTaskMessage);
             var jobSuccess = GetMessageCount(lines, DoneActionMessage);
diff --git a/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/TestFailUpdateEvaluator.cs b/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/TestFailUpdateEvaluator.cs
index 213cac4..239ab1c 100644
--- a/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/TestFailUpdateEvaluator.cs
+++ b/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/TestFailUpdateEvaluator.cs
@@ -59,7 +59,7 @@
                 NumberOfRetry,
                 testFolder);
             string[] lines = ReadLogFile(DriverStdout, "driver", testFolder, 240);
-            var completedTaskCount = GetMessageCount(lines, "Received ICompletedTask");
+            var completedTaskCount = GetMessageCount(lines, CompletedTaskMessage);
             var runningTaskCount = GetMessageCount(lines, RunningTaskMessage);
             var failedEvaluatorCount = GetMessageCount(lines, FailedEvaluatorMessage);
             var failedTaskCount = GetMessageCount(lines, FailedTaskMessage);
diff --git a/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/TestFailUpdateEvaluatorOnWaitingForEvaluator.cs b/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/TestFailUpdateEvaluatorOnWaitingForEvaluator.cs
index b12b1ef..8c09d28 100644
--- a/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/TestFailUpdateEvaluatorOnWaitingForEvaluator.cs
+++ b/lang/cs/Org.Apache.REEF.Tests/Functional/IMRU/TestFailUpdateEvaluatorOnWaitingForEvaluator.cs
@@ -50,7 +50,7 @@
             TestBroadCastAndReduce(false, numTasks, chunkSize, dims, iterations, mapperMemory, updateTaskMemory, numberOfRetryInRecovery, testFolder);
 
             string[] lines = ReadLogFile(DriverStdout, "driver", testFolder, 120);
-            var jobFailure = GetMessageCount(lines, IMRUDriver<int[], int[], int[], int[]>.FailActionPrefix);
+            var jobFailure = GetMessageCount(lines, FailedActionMessage);
             Assert.True(jobFailure > 0);
             CleanUp(testFolder);
         }