YARN-590. Added an optional mesage to be returned by ResourceMaanger when RM asks an RM to shutdown/resync etc so that NMs can log this message locally for better debuggability. Contributed by Mayank Bansal.
svn merge --ignore-ancestry -c 1481234 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1481235 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/branch-2' into branch-2-gd
Merge remote branch 'origin/branch-2-gd' into fb-HADOOP-7435-branch-2-gd