Unconfiguring a vn while it is mounted

[Rumko]

I was able to test (unintentionally), that you can vnconfig -u a vn that is
still mounted without any errors (it just works)
.. the problem is, you can't unmount it anymore (even -f doesn't
work ... "umount -f /mnt" "umount: unmount of /mnt failed: Device not
configured").
-- 
Regards,
Rumko