HADOOP-9948. Merging change r1526607 from branch-2 to branch-2.1-beta

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.1-beta@1526608 13f79535-47bb-0310-9956-ffa450edef68
HDFS-5258. Merging change r1526611 from branch-2 to branch-2.1-beta

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.1-beta@1526612 13f79535-47bb-0310-9956-ffa450edef68
HDFS-5186. Merging change r1526617 from branch-2 to branch-2.1-beta

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.1-beta@1526622 13f79535-47bb-0310-9956-ffa450edef68
MAPREDUCE-5525. Merging change r1526625 from branch-2 to branch-2.1-beta

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.1-beta@1526630 13f79535-47bb-0310-9956-ffa450edef68