merge MAPREDUCE-5329. Allow MR applications to use additional AuxServices, which are compatible with the default MapReduce shuffle. Contributed by Avner BenHanoch.


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1531742 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-9166-branch-2-gd