HDFS-5393. Merge change r1543248 from trunk.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1543249 13f79535-47bb-0310-9956-ffa450edef68
YARN-709. Added tests to verify validity of delegation tokens and logging of appsummary after RM restart. Contributed by Jian He.
svn merge --ignore-ancestry -c 1543269 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1543271 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/branch-2' into branch-2-gd
Merge remote branch 'origin/branch-2-gd' into fb-MAPREDUCE-4884-branch-2-gd