Merge -r 1475669:1475670 from trunk to branch-2. Fixes: YARN-595. Refactor fair scheduler to use common Resources. Contributed by Sandy Ryza.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1475672 13f79535-47bb-0310-9956-ffa450edef68