YARN-1446. Changed client API to retry killing application till RM acknowledges so as to account for RM crashes/failover. Contributed by Jian He.
svn merge --ignore-ancestry -c 1551444 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1551445 13f79535-47bb-0310-9956-ffa450edef68