Use tryFailure to support calling jobFailed multiple times

Author: zsxwing

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

@@ -62,15 +62,15 @@ private[spark] class JobWaiter[T](
     if (finishedTasks == totalTasks) {
       _jobFinished = true
       jobResult = JobSucceeded
-      promise.success()
+      promise.trySuccess()
       this.notifyAll()
     }
   }
 
   override def jobFailed(exception: Exception): Unit = synchronized {
     _jobFinished = true
     jobResult = JobFailed(exception)
-    promise.failure(exception)
+    promise.tryFailure(exception)
     this.notifyAll()
   }