When a class is going passive, it should update its cl_vt first
to be consistent with the last dequeue operation.

Otherwise its cl_vt will be one packet behind and parent's cvtmax might
not be updated as well.

One possible side effect is if some class goes passive and subsequently
goes active /without/ its parent going passive - with cl_vt lagging one
packet behind - comparison made in init_vf() will be affected (same
period).
Signed-off-by: Michal Soltys <soltys@ziu.info>
Signed-off-by: David S. Miller <davem@davemloft.net>