Now, virtio-scsi disks use the same name as virtio-blk, e.g., vblk0,
vlbk1. If both scsi and blk are added to guest, they share the global disk
index number.

Signed-off-by: Asias He <asias@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>