block: Always pass NULL as drv for bdrv_open() Change all callers of bdrv_open() to pass the driver name in the options QDict instead of passing its BlockDriver pointer. Signed-off-by: Max Reitz <mreitz@redhat.com> Reviewed-by: Alberto Garcia <berto@igalia.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>