Change the behaviour of netem's delayed packets queue to make it work better
with TBF and other rate control disciplines.

Now, packets are put in the delayed queue and held there until the next timer interval,
then moved to the underlying qdisc. qlen is set to match the available packets in 
the underlying discipline (and not count those waiting). Previously, netem would perturb
the rate control disciplines because of rescheduling and moving packets in
the dequeue handler.
Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>