Merge -r 1476394:1476395 from trunk onto branch-2. Fixes HDFS-2576.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1480135 13f79535-47bb-0310-9956-ffa450edef68
Merge -r 1477848:1477849 from trunk onto branch-2. Fixes HDFS-4778.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1480136 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/branch-2' into branch-2-gd
Merge remote branch 'origin/branch-2-gd' into fb-MAPREDUCE-4884-branch-2-gd