HDFS-4693. Merge r1468457 from trunk.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1486098 13f79535-47bb-0310-9956-ffa450edef68
HADOOP-8562. Merge r1469996 for HADOOP-9488, r1469998 for YARN-593

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1486101 13f79535-47bb-0310-9956-ffa450edef68
MAPREDUCE-4987. Merge r1470003  from trunk

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1486106 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/branch-2' into branch-2-gd
Merge remote branch 'origin/branch-2-gd' into fb-YAHOO-226-branch-2-gd