sctp: fix dst leak

Commit 0ca50d12 failed to release the reference to dst entries that
it decided to skip.

Fixes: 0ca50d12 ("sctp: fix src address selection if using secondary addresses")
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>