svn merge -c 1506675 merging from trunk to branch-2 to fix YARN-968.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1506678 13f79535-47bb-0310-9956-ffa450edef68
YARN-873. Merge r1506732 from trunk to branch-2 for YARNClient.getApplicationReport(unknownAppId) returns a null report (Xuan Gong via bikas)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1506736 13f79535-47bb-0310-9956-ffa450edef68
Merge r1506750 from trunk to branch-2 for YARN-875. Application can hang if AMRMClientAsync callback thread has exception (Xuan Gong via bikas)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1506752 13f79535-47bb-0310-9956-ffa450edef68