YARN-1852. Fixed RMAppAttempt to not resend AttemptFailed/AttemptKilled events to already recovered Failed/Killed RMApps. Contributed by Rohith Sharmaks

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1580997 13f79535-47bb-0310-9956-ffa450edef68