blk_insert_request will do the right thing and either unplug the queue or
call the request_fn, so users of scsi_do_req do not need to call
generic_unplug_device themselves. The attached patch just removes that
call from scsi_lib.c and the sg driver after they do a scsi_do_req.
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>