sctp: Fix SNMP number of SCTP_MIB_ABORTED during violation handling.

If ABORT chunks require authentication and a protocol violation
is triggered, we do not tear down the association.  Subsequently,
we should not increment SCTP_MIB_ABORTED.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>