HDFS-5252. Merging change r1539740 form trunk

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1539742 13f79535-47bb-0310-9956-ffa450edef68
HDFS-5443. Merge change r1539754 from trunk.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1539758 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