Merge change r1524581 from trunk: move HDFS-5122 from Release 2.1.1-beta to Release 2.3.0 in CHANGES.txt

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1524583 13f79535-47bb-0310-9956-ffa450edef68