HDFS-6617. Merging change r1608522 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1608523 13f79535-47bb-0310-9956-ffa450edef68
HADOOP-10782. Merge r1608539 from trunk.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1608541 13f79535-47bb-0310-9956-ffa450edef68
MAPREDUCE-5868. Fixed an issue with TestPipeApplication that was causing the nightly builds to fail. Contributed by Akira Ajisaka.
svn merge --ignore-ancestry -c 1608579 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1608580 13f79535-47bb-0310-9956-ffa450edef68
MAPREDUCE-5866. Merging change r1608585 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1608588 13f79535-47bb-0310-9956-ffa450edef68
MAPREDUCE-5517. Fixed MapReduce ApplicationMaster to not validate reduce side resource configuration for deciding uber-mode on map-only jobs. Contributed by Siqi Li.
svn merge --ignore-ancestry -c 1608595 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1608596 13f79535-47bb-0310-9956-ffa450edef68