net-sched: Fix actions flushing

Flushing of actions has been broken since we changed
the semantics of netlink parsed tb[X] to mean X is an attribute type.
This makes the flushing work.

Signed-off-by: Jamal Hadi Salim <hadi@cyberus.ca>
Signed-off-by: David S. Miller <davem@davemloft.net>