ORNL-23 avoid unnecessary CMD lock contention in LMV

ORNL-23 avoid unnecessary CMD lock contention in LMV

There are some redundant lock operations in LMV layer which is only
useful under old CMD mode. We should avoid those lock operations to
reduce unnecessary lock contention.

Change-Id: I2ad1ba728da39ce69b0e521ab3a992dd2b253f2e
Signed-off-by: nasf <yong.fan@whamcloud.com>
Reviewed-on: http://review.whamcloud.com/1226
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Lai Siyao <laisiyao@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>