LU-7791 ldlm: signal vs CP callback race

LU-7791 ldlm: signal vs CP callback race

a lock isn't canceled on the server on reception
of a signal on the client when it is blocked waiting
for a lock to be granted, thus client is evicted for
not responding to LDLM_FL_AST_SENT.

Seagate-bug-id: MRP-3314
Change-Id: Ie025bb58b13fb2d741119f74c87439f917983268
Signed-off-by: Andriy Skulysh <andriy.skulysh@seagate.com>
Reviewed-on: http://review.whamcloud.com/18498
Tested-by: Jenkins
Reviewed-by: Vitaly Fertman <vitaly.fertman@seagate.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Chris Horn <hornc@cray.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>