ORNL-27: Cancel on completion lock on the MGS

We should cancel the recover/config LCK_EX lock immediately
when they are granted to accelerate enqueue process.

Also, it doesn't make sense to add mgc recover/config lock into
LRU list because these kinds of lock would never be canceled
voluntarily. Restore LDLM_FL_NO_LRU flag and apply it for mgc
lock.

Signed-off-by: Jinshan Xiong <jay@whamcloud.com>
Change-Id: I369b57ca4780b0bfa07d33b4423b468481263ade
Reviewed-on: http://review.whamcloud.com/1261
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>