This moves as much as possible of the processing of the 'media' option
to drive_init so that it can only be accessed using legacy functions,
but never with anything blockdev-add related.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NBenoit Canet <benoit@irqsave.net>
Reviewed-by: NEric Blake <eblake@redhat.com>