HADOOP-9787. ShutdownHelper util to shutdown threads and threadpools. (Karthik Kambatla via Sandy Ryza)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1509053 13f79535-47bb-0310-9956-ffa450edef68
YARN-502. Fixed a state machine issue with RMNode inside ResourceManager which was crashing scheduler. Contributed by Mayank Bansal.
svn merge --ignore-ancestry -c 1509060 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1509061 13f79535-47bb-0310-9956-ffa450edef68
HADOOP-9758.  Provide configuration option for FS/FC symlink resolution.  (Andrew Wang via Colin Patrick McCabe)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1509065 13f79535-47bb-0310-9956-ffa450edef68