[SCSI] scsi_dh_hp_sw: fix deadlock in start_stop_endio

The use of blk_execute_rq_nowait() implies __blk_put_request() is needed
in start_stop_endio() rather than blk_put_request() --
blk_finish_request() is called with queue lock already held.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>