HADOOP-9948. Merging change r1526606 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1526607 13f79535-47bb-0310-9956-ffa450edef68
HDFS-5258. Merging change r1526610 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1526611 13f79535-47bb-0310-9956-ffa450edef68
HDFS-5186. Merging change r1526615 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1526617 13f79535-47bb-0310-9956-ffa450edef68
MAPREDUCE-5525. Merging change r1526624 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1526625 13f79535-47bb-0310-9956-ffa450edef68