SPARK-5613: Catch the ApplicationNotFoundException exception to avoid thread from getting killed on yarn restart.

[SPARK-5613] Added a  catch block to catch the ApplicationNotFoundException. Without this catch block the thread gets killed on occurrence of this exception. This Exception occurs when yarn restarts and tries to find an application id for a spark job which got interrupted due to yarn getting stopped.
See the stacktrace in the bug for more details.

Author: Kashish Jain <[email protected]>

Closes apache#4392 from kasjain/branch-1.2 and squashes the following commits:

4831000 [Kashish Jain] SPARK-5613: Catch the ApplicationNotFoundException exception to avoid thread from getting killed on yarn restart.

Author: kasjain

yarn/src/main/scala/org/apache/spark/scheduler/cluster/YarnClientSchedulerBackend.scala

@@ -20,6 +20,7 @@ package org.apache.spark.scheduler.cluster
 import scala.collection.mutable.ArrayBuffer
 
 import org.apache.hadoop.yarn.api.records.{ApplicationId, YarnApplicationState}
+import org.apache.hadoop.yarn.exceptions.ApplicationNotFoundException
 
 import org.apache.spark.{SparkException, Logging, SparkContext}
 import org.apache.spark.deploy.yarn.{Client, ClientArguments}
@@ -133,8 +134,14 @@ private[spark] class YarnClientSchedulerBackend(
     val t = new Thread {
       override def run() {
         while (!stopping) {
-          val report = client.getApplicationReport(appId)
-          val state = report.getYarnApplicationState()
+          var state: YarnApplicationState = null
+          try {
+            val report = client.getApplicationReport(appId)
+            state = report.getYarnApplicationState()
+          } catch {
+            case e: ApplicationNotFoundException =>
+              state = YarnApplicationState.KILLED
+          }
           if (state == YarnApplicationState.FINISHED ||
             state == YarnApplicationState.KILLED ||
             state == YarnApplicationState.FAILED) {