merge YARN-716 from trunk. Fixed unit test failures - TestDistributedShell and TestUnmanagedAMLauncher. Contributed by Vinod Kumar Vavilapalli.


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1485580 13f79535-47bb-0310-9956-ffa450edef68