Fix test suite issue after moving aggregator to Shuffle reader and writer

Author: jerryshao

core/src/test/scala/org/apache/spark/scheduler/SparkListenerSuite.scala

@@ -181,7 +181,7 @@ class SparkListenerSuite extends FunSuite with LocalSparkContext with Matchers
     assert(sc.listenerBus.waitUntilEmpty(WAIT_TIMEOUT_MILLIS))
     listener.stageInfos.size should be {2} // Shuffle map stage + result stage
     val stageInfo3 = listener.stageInfos.keys.find(_.stageId == 2).get
-    stageInfo3.rddInfos.size should be {2} // ShuffledRDD, MapPartitionsRDD
+    stageInfo3.rddInfos.size should be {1} // ShuffledRDD
     stageInfo3.rddInfos.forall(_.numPartitions == 4) should be {true}
     stageInfo3.rddInfos.exists(_.name == "Trois") should be {true}
   }