corrected spelling in CHANGES.txt for MAPREDUCE-4397 entry.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1.1@1439266 13f79535-47bb-0310-9956-ffa450edef68
finish submission for MAPREDUCE-4396.  Include unit test from HADOOP-8734.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1.1@1439273 13f79535-47bb-0310-9956-ffa450edef68