[SPARK-6018] [YARN] NoSuchMethodError in Spark app is swallowed by YARN AM

Author: Cheolsoo Park <cheolsoop@netflix.com>

Closes #4773 from piaozhexiu/SPARK-6018 and squashes the following commits:

2a919d5 [Cheolsoo Park] Rename e with cause to avoid duplicate names
1e71d2d [Cheolsoo Park] Replace placeholder with throwable
eb5750d [Cheolsoo Park] NoSuchMethodError in Spark app is swallowed by YARN AM

(cherry picked from commit 5f3238b)
Signed-off-by: Andrew Or <andrew@databricks.com>

Author: Cheolsoo Park

yarn/common/src/main/scala/org/apache/spark/deploy/yarn/ApplicationMaster.scala

@@ -446,12 +446,12 @@ private[spark] class ApplicationMaster(args: ApplicationMasterArguments,
             e.getCause match {
               case _: InterruptedException =>
                 // Reporter thread can interrupt to stop user class
-              case e: Exception =>
+              case cause: Throwable =>
                 finish(FinalApplicationStatus.FAILED,
                   ApplicationMaster.EXIT_EXCEPTION_USER_CLASS,
-                  "User class threw exception: " + e.getMessage)
+                  "User class threw exception: " + cause.getMessage)
                 // re-throw to get it logged
-                throw e
+                throw cause
             }
         }
       }