iotests: fix nbd test 233 to work correctly with raw images

The first qemu-io command must honour the $IMGFMT that is set rather
than hardcoding qcow2. The qemu-nbd commands should also set $IMGFMT
to avoid the insecure format probe warning.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
1 file changed