Fix CHANGES.txt in hdfs

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1506561 13f79535-47bb-0310-9956-ffa450edef68
svn merge -c 1506675 merging from trunk to branch-2 to fix YARN-968.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1506678 13f79535-47bb-0310-9956-ffa450edef68