Merge HDFS-4949 changes from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1560522 13f79535-47bb-0310-9956-ffa450edef68
YARN-1607. TestRM relies on the scheduler assigning multiple containers in a single node update (Sandy Ryza)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1560534 13f79535-47bb-0310-9956-ffa450edef68
HDFS-5806. Balancer should set soTimeout to avoid indefinite hangs. Contributed by Nathan Roberts.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1560549 13f79535-47bb-0310-9956-ffa450edef68
YARN-1623. Include queue name in RegisterApplicationMasterResponse (Sandy Ryza)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1560555 13f79535-47bb-0310-9956-ffa450edef68