cdrom_id: Fix state for fresh DVD-RW

cdrom_id: Fix state for fresh DVD-RW

Fresh DVD-RW in restricted overwite mode reports itself as "appendable"; change
it to "blank" to make it consistent with what gets reported after blanking, and
what userspace expects.

For the exotic case where some uses multi-track recording on a DVD-RW in
sequential mode, we need to tell apart sequential and restricted overwrite
modes, so keep separate states for them internally.

Signed-off-by: Martin Pitt <martin.pitt@ubuntu.com>