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
MAPREDUCE-5213. Re-assess TokenCache methods marked @Private. (kkambatl via tucu)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1506759 13f79535-47bb-0310-9956-ffa450edef68
HADOOP-9701. mvn site ambiguous links in hadoop-common. (kkambatl via tucu)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1506765 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/branch-2' into branch-2-gd
Merge remote branch 'origin/branch-2' into branch-2-gd
Merge remote branch 'origin/branch-2-gd' into fb-YAHOO-271-branch-2-gd