This arg is always '0', so remove it.
Consequently, OBD_BRW_NOCACHE is never set, and
cl_dirty_transit and obd_dirty_transit_pages
are never non-zero.
So they can be removed as well.

Linux-commit: 8d1057264a75

Test-Parameters: trivial
Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: Ia047affc33fb9277e6c28a8f6d7d088c385b51a8
Reviewed-on: https://review.whamcloud.com/36319


Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Shaun Tancheff <stancheff@cray.com>
Reviewed-by: Ben Evans <bevans@cray.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>