YARN-1964. Create Docker analog of the LinuxContainerExecutor in YARN
YARN-2841. RMProxy should retry EOFException.  Contributed by Jian He
YARN-2843. Fixed NodeLabelsManager to trim inputs for hosts and labels so as to make them work correctly. Contributed by Wangda Tan.

(cherry picked from commit 0fd97f9c1989a793b882e6678285607472a3f75a)

Conflicts:
	hadoop-yarn-project/CHANGES.txt
YARN-2843. Merging to branch-2.6 for hadoop-2.6.0-rc1.

(cherry picked from commit 51957ca81886ac3553c44848631fdf53766a25ae)

Conflicts:
	hadoop-yarn-project/CHANGES.txt
YARN-2794. Fixed log messages about distributing system-credentials. Contributed by Jian He.

(cherry picked from commit be7bf956e96dd0fd9b521ca71df9124b9cc5ebd0)