Merge r1594123 from trunk. YARN-1976. Fix CHANGES.txt for YARN-1976.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1594124 13f79535-47bb-0310-9956-ffa450edef68
Merge. HDFS-6367. EnumSetParam$Domain#parse fails for parameter containing more than one enum. Contributed by Yi Liu.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1594151 13f79535-47bb-0310-9956-ffa450edef68