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>
diff --git a/src/vnet/sctp/sctp_packet.h b/src/vnet/sctp/sctp_packet.h
index b831d24..3ca05b5 100644
--- a/src/vnet/sctp/sctp_packet.h
+++ b/src/vnet/sctp/sctp_packet.h
@@ -163,7 +163,8 @@
   COOKIE_ACK,
   ECNE,
   CWR,
-  SHUTDOWN_COMPLETE
+  SHUTDOWN_COMPLETE,
+  UNKNOWN
 } sctp_chunk_type;
 
 /*