Merge r1503526 from trunk to branch-2 for YARN-521. Augment AM - RM client module to be able to request containers only at specific locations (Sandy Ryza via bikas)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1503527 13f79535-47bb-0310-9956-ffa450edef68