HDFS-5375. Merging change r1533165 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1533166 13f79535-47bb-0310-9956-ffa450edef68
HDFS-5379. Merge change r1533181 from trunk.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1533182 13f79535-47bb-0310-9956-ffa450edef68
HDFS-5336. Merging change r1533183 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1533184 13f79535-47bb-0310-9956-ffa450edef68
HADOOP-10055. Merging change r1533188 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1533189 13f79535-47bb-0310-9956-ffa450edef68