LU-1306 ldlm: LBUG at ldlm_lock.c:213

LU-1306 ldlm: LBUG at ldlm_lock.c:213

Protect l_flags with locking to prevent race on
signal reception.

Xyratex-bug-id: MRP-420
Signed-off-by: Andriy Skulysh <Andriy_Skulysh@xyratex.com>
Reviewed-by: Vitaly Fertman <vitaly_fertman@xyratex.com>
Reviewed-by: Iurii Golovach <iurii_golovach@xyratex.com>
Change-Id: Ifbf9e668bfeba30c9f9f206086186ad7d499a871
Reviewed-on: http://review.whamcloud.com/2511
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>