YARN-625. Move the utility method unwrapAndThrowException from YarnRemoteExceptionPBImpl to RPCUtil. Contributed by Siddharth Seth.
svn merge --ignore-ancestry -c 1478594 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1478595 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/branch-2' into branch-2-gd
Merge remote branch 'origin/branch-2-gd' into fb-YARN-474-branch-2-gd