MAPREDUCE-5086. MR app master deletes staging dir when sent a reboot command from the RM. Contributed by Jian He


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1465674 13f79535-47bb-0310-9956-ffa450edef68
Merge -c 1465731 from trunk to branch-2 for YARN-479. NM retry behavior for connection to RM should be similar for lost heartbeats (Jian He via bikas)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1465733 13f79535-47bb-0310-9956-ffa450edef68
HDFS-3981. Fix handling of FSN lock in getBlockLocations. Contributed by Xiaobo Peng and Todd Lipcon.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1465752 13f79535-47bb-0310-9956-ffa450edef68