HADOOP-8562. CHANGES.txt cleanup related to merging the related jiras to branch-2

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1486384 13f79535-47bb-0310-9956-ffa450edef68
HDFS-4825. Merge change 1486386 from trunk

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1486387 13f79535-47bb-0310-9956-ffa450edef68