Merge r1594795 from trunk: MAPREDUCE-5861. finishedSubMaps field in LocalContainerLauncher does not need to be volatile. (Contributed by Tsuyoshi OZAWA)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1594797 13f79535-47bb-0310-9956-ffa450edef68