Updating branch-2.3's YARN's CHANGES.txt to reflect the recent rebase of unreleased 2.3 to more latest branch-2.
Fixing entry for MAPREDUCE-5732 in trunk and branch-2.


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1562949 13f79535-47bb-0310-9956-ffa450edef68