Merge -c 1430688 from trunk to branch-2 to fix MAPREDUCE-4520. Added support for MapReduce applications to request for CPU cores along-with memory post YARN-2. Contributed by Arun C. Murthy.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1430690 13f79535-47bb-0310-9956-ffa450edef68