sctp: check assoc before SCTP_ADDR_{MADE_PRIM, ADDED} event

sctp: check assoc before SCTP_ADDR_{MADE_PRIM, ADDED} event

Make sure SCTP_ADDR_{MADE_PRIM,ADDED} are sent only for associations
that have been established.

These events are described in rfc6458#section-6.1
SCTP_PEER_ADDR_CHANGE:
This tag indicates that an address that is
part of an existing association has experienced a change of
state (e.g., a failure or return to service of the reachability
of an endpoint via a specific transport address).

Signed-off-by: Jonas Falkevik <jonas.falkevik@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Reviewed-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>