YARN-873. YARNClient.getApplicationReport(unknownAppId) returns a null report (Xuan Gong via bikas)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1506732 13f79535-47bb-0310-9956-ffa450edef68
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/trunk@1506750 13f79535-47bb-0310-9956-ffa450edef68
Merge remote-tracking branch upstream/$:{upbranch}