Fixed bug where task set managers are added to queue twice

This bug leads to a small performance hit because task
set managers will get offered each rejected resource
offer twice, but doesn't lead to any incorrect functionality.

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

@@ -592,7 +592,7 @@ private[spark] class TaskSetManager(
   override def removeSchedulable(schedulable: Schedulable) {}
 
   override def getSortedTaskSetQueue(): ArrayBuffer[TaskSetManager] = {
-    var sortedTaskSetQueue = ArrayBuffer[TaskSetManager](this)
+    var sortedTaskSetQueue = new ArrayBuffer[TaskSetManager]()
     sortedTaskSetQueue += this
     sortedTaskSetQueue
   }