cciss: Set the performant mode bit in the scsi half of the driver

cciss: Set the performant mode bit in the scsi half of the driver
In a couple of places, the performant mode bit wasn't being set in
the scsi half of the driver, causing commands to seem to hang.  Use
enqueue_cmd_and_start_io() where appropriate.  This fixes a bug that

	echo engage scsi > /proc/driver/cciss/cciss0

would hang.

Signed-off-by: Stephen M. Cameron <scameron@beardog.cce.hp.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>