svn merge -c 1300750 FIXES: MAPREDUCE-4007. JobClient getJob(JobID) should return NULL if the job does not exist (for backwards compatibility). Contributed by Alejandro Abdelnur


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-0.23@1450951 13f79535-47bb-0310-9956-ffa450edef68