HDFS-6265. Merging change r1588995 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1588998 13f79535-47bb-0310-9956-ffa450edef68
HDFS-6178. Merge r1589002 from trunk.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1589003 13f79535-47bb-0310-9956-ffa450edef68
YARN-1970. Merging change r1589001 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1589004 13f79535-47bb-0310-9956-ffa450edef68
MAPREDUCE-5852. Merging change r1589006 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1589007 13f79535-47bb-0310-9956-ffa450edef68