xt_tee: use skb_dst_drop()

After commit 7fee226a (net: add a noref bit on skb dst), its wrong to
use : dst_release(skb_dst(skb)), since we could decrement a refcount
while skb dst was not refcounted.

We should use skb_dst_drop(skb) instead.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>