[SCSI] libsas: fix deref before check in commit 70b25f89

commit 70b25f89
Author: Tejun Heo <tj@kernel.org>
Date:   Thu Apr 15 09:00:08 2010 +0900

    [SCSI] fix locking around blk_abort_request()

Introduced a reference before check problem, fix this by moving the
lock shorthand code to be right at the point of actual use.

Reported-by: Dan Carpenter <error27@gmail.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Stable Tree <stable@kernel.org>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>