YARN-2562. Changed ContainerId#toString() to be more readable. Contributed by Tsuyoshi OZAWA
(cherry picked from commit eb6ce5e97c6a379caf9de0b34cc7770c4447bb1a)
YARN-2468. Enhanced NodeManager to support log handling APIs (YARN-2569) for use by long running services. Contributed by Xuan Gong.

(cherry picked from commit 34cdcaad71cad76c0874a4e5266b4074009d2ffc)