scsi_id: switch temporary node creation to /dev

scsi_id: switch temporary node creation to /dev

/tmp is not writable on most systems, so just use /dev to create a
temporary node. If called from a udev rule, "-d $tempnode" should be
used and udev will create a temporary node and pass the name before
calling scsi_id.
Also remove gen_scsi_id_udev_rules.sh per Patrick's request, as it's
no longer needed with the persistent disk links.

Signed-off-by: Kay Sievers <kay.sievers@suse.de>