PIG-4935: TEZ_USE_CLUSTER_HADOOP_LIBS is always set to true (rohini)

git-svn-id: https://svn.apache.org/repos/asf/pig/trunk@1754185 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/CHANGES.txt b/CHANGES.txt
index 541b03e..7ab71bd 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -38,6 +38,8 @@
  
 BUG FIXES
 
+PIG-4935: TEZ_USE_CLUSTER_HADOOP_LIBS is always set to true (rohini)
+
 PIG-4961: CROSS followed by LIMIT inside nested foreach drop data from result (rohini)
 
 PIG-4960: Split followed by order by/skewed join is skewed in Tez (rohini)
diff --git a/src/org/apache/pig/backend/hadoop/executionengine/tez/TezLauncher.java b/src/org/apache/pig/backend/hadoop/executionengine/tez/TezLauncher.java
index 536b1a1..adb3486 100644
--- a/src/org/apache/pig/backend/hadoop/executionengine/tez/TezLauncher.java
+++ b/src/org/apache/pig/backend/hadoop/executionengine/tez/TezLauncher.java
@@ -166,7 +166,7 @@
         tezStats = new TezPigScriptStats(pc);
         PigStats.start(tezStats);
 
-        conf.set(TezConfiguration.TEZ_USE_CLUSTER_HADOOP_LIBS, "true");
+        conf.setIfUnset(TezConfiguration.TEZ_USE_CLUSTER_HADOOP_LIBS, "true");
         TezJobCompiler jc = new TezJobCompiler(pc, conf);
         TezPlanContainer tezPlanContainer = compile(php, pc);