Merge -c 1470216 from trunk to branch-2 to fix MAPREDUCE-5066. Added a timeout for the job.end.notification.url. Contributed by Ivan Mitic.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1470217 13f79535-47bb-0310-9956-ffa450edef68