[MINOR] Check for extra values in test matrix comparison.

In the case of expected matrices with zero values, TestUtils was not
correctly checking whether the actual test output matrix does have
values in these places.

Closes #987
diff --git a/src/test/java/org/apache/sysds/test/TestUtils.java b/src/test/java/org/apache/sysds/test/TestUtils.java
index 857d2fb..8819f56 100644
--- a/src/test/java/org/apache/sysds/test/TestUtils.java
+++ b/src/test/java/org/apache/sysds/test/TestUtils.java
@@ -217,10 +217,14 @@
 
 				readValuesFromFileStreamAndPut(outIn, actualValues);
 			}
-			
+
+			Set<CellIndex> allKeys = new HashSet<>();
+			allKeys.addAll(expectedValues.keySet());
+			if(expectedValues.size() != actualValues.size())
+				allKeys.addAll(actualValues.keySet());
 
 			int countErrors = 0;
-			for (CellIndex index : expectedValues.keySet()) {
+			for (CellIndex index : allKeys) {
 				Double expectedValue = expectedValues.get(index);
 				Double actualValue = actualValues.get(index);
 				if (expectedValue == null)
@@ -346,8 +350,12 @@
 
 		readActualAndExpectedFile(null, expectedFile, actualDir, expectedValues, actualValues);
 
+		Set<CellIndex> allKeys = new HashSet<>();
+		allKeys.addAll(expectedValues.keySet());
+		if(expectedValues.size() != actualValues.size())
+			allKeys.addAll(actualValues.keySet());
 		int countErrors = 0;
-		for(CellIndex index : expectedValues.keySet()) {
+		for(CellIndex index : allKeys) {
 			Double expectedValue = (Double) expectedValues.get(index);
 			Double actualValue = (Double) actualValues.get(index);
 			if(expectedValue == null)
@@ -383,8 +391,12 @@
 
 		readActualAndExpectedFile(schema, expectedFile, actualDir, expectedValues, actualValues);
 
+		Set<CellIndex> allKeys = new HashSet<>();
+		allKeys.addAll(expectedValues.keySet());
+		if(expectedValues.size() != actualValues.size())
+			allKeys.addAll(actualValues.keySet());
 		int countErrors = 0;
-		for(CellIndex index : expectedValues.keySet()) {
+		for(CellIndex index : allKeys) {
 			Object expectedValue = expectedValues.get(index);
 			Object actualValue = actualValues.get(index);
 
@@ -1107,9 +1119,13 @@
 				FSDataInputStream fsout = fs.open(file.getPath());
 				readValuesFromFileStream(fsout, actualValues);
 			}
+			Set<CellIndex> allKeys = new HashSet<>();
+			allKeys.addAll(expectedValues.keySet());
+			if(expectedValues.size() != actualValues.size())
+				allKeys.addAll(actualValues.keySet());
 
 			int countErrors = 0;
-			for (CellIndex index : expectedValues.keySet()) {
+			for (CellIndex index : allKeys) {
 				Double expectedValue = expectedValues.get(index);
 				Double actualValue = actualValues.get(index);
 				if (expectedValue == null)