SCTP: fix corrupted buffers seen in output node

SCTP: fix corrupted buffers seen in output node

The issue observed in the output-node was actually
caused by one of the input-node pushing buffers to
the output node when not required. That is the case
with the parsing/handling of incoming packets like
the COOKIE_ACK, HEARTBEAT_ACK, DATA, SACK which do
not require a response to be sent to the other peer.
In all the mentioned cases the packets (buffers) need
to be consumed and dropped instead of heading to the
output-node.

Change-Id: I3dcbe5de1cedb2ab8b06fff4364749b525cc7ac6
Signed-off-by: Marco Varlese <marco.varlese@suse.com>