svn merge -c 1506675 merging from trunk to branch-2.1-beta to fix YARN-968.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.1-beta@1506679 13f79535-47bb-0310-9956-ffa450edef68
YARN-873. Merge r1506736 from branch-2 to branch-2.1-beta 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-2.1-beta@1506744 13f79535-47bb-0310-9956-ffa450edef68