LU-925 agl: async glimpse lock process in CLIO stack

LU-925 agl: async glimpse lock process in CLIO stack

Adjust CLIO lock state machine for supporting:
1. unuse lock in non-hold state.
2. re-enqueue non-granted glimpse lock.

Signed-off-by: Fan Yong <yong.fan@whamcloud.com>
Change-Id: I9de8939a398d7b4c7062e6c5859bca06deddd089
Reviewed-on: http://review.whamcloud.com/1243
Reviewed-by: Niu Yawei <niu@whamcloud.com>
Tested-by: Hudson
Reviewed-by: Jinshan Xiong <jinshan.xiong@whamcloud.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>