YARN-1954. Added waitFor to AMRMClient(Async). Contributed by Tsuyoshi Ozawa.
svn merge --ignore-ancestry -c 1617002 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1617003 13f79535-47bb-0310-9956-ffa450edef68