scsi_debug: uuid for lu name

Permit changing of a LU name from a (fake) IEEE registered NAA (5) to a
locally assigned UUID. Using a UUID (RFC 4122) for a SCSI designation
descriptor (e.g. a LU name) was added in spc5r08.pdf (a draft INCITS
standard) on 25 January 2016. Add parameter uuid_ctl to use a separate
UUID for each LU (storage device) name.  Additional option for all LU
names to have the same UUID (since their storage is shared). Previous
action of using NAA identifier for LU name remains the default.

Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>