LU-4405 mdc: use ibits_known mask for lock match

Before revalidating a lock on the client, mask the lock bits against
the lock bits supported by the server (ibits_known), so newer clients
will find valid locks given by older server versions.

Xyratex-bug-id: MRP-1583

Signed-off-by: Patrick Farrell <paf@cray.com>
Signed-off-by: Alexey Lyashkov <alexey_lyashkov@xyratex.com>
Change-Id: I359b87e4bdc7b930e51538a4a854c47e87dd0520
Reviewed-on: http://review.whamcloud.com/8636
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>