HDFS-4052. Merge r1398631 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1595063 13f79535-47bb-0310-9956-ffa450edef68
HDFS-6362. Merge r1595056 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1595066 13f79535-47bb-0310-9956-ffa450edef68