[CORE] SPARK-6880: Fixed null check when all the dependent stages are...

[CORE] SPARK-6880: Fixed null check when all the dependent stages are cancelled due to previous stage failure

Fixed null check when all the dependent stages are cancelled due to previous stage failure. This happens when one of the executor node goes down and all the dependent stages are cancelled.

Author: pankaj arora <pankaj.arora@guavus.com>

Closes #5494 from pankajarora12/NEWBRANCH and squashes the following commits:

55ba5e3 [pankaj arora] [CORE] SPARK-6880: Fixed null check when all the dependent stages are cancelled due to previous stage failure
4575720 [pankaj arora] [CORE] SPARK-6880: Fixed null check when all the dependent stages are cancelled due to previous stage failure

core/src/main/scala/org/apache/spark/scheduler/DAGScheduler.scala

@@ -818,12 +818,7 @@ class DAGScheduler(
       }
     }
 
-    val properties = if (jobIdToActiveJob.contains(jobId)) {
-      jobIdToActiveJob(stage.jobId).properties
-    } else {
-      // this stage will be assigned to "default" pool
-      null
-    }
+    val properties = jobIdToActiveJob.get(stage.jobId).map(_.properties).orNull
 
     runningStages += stage
     // SparkListenerStageSubmitted should be posted before testing whether tasks are