Merge -r 1430362:1430363 from trunk to branch-2. Fixes: MAPREDUCE-4278. Cannot run two local jobs in parallel from the same gateway. Contributed by Sandy Ryza.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1430369 13f79535-47bb-0310-9956-ffa450edef68