iuup: Check for IuUP Initialization retrans

Since libosmocore.git Change-Id
I5cb740702805693cc7f0a550e2e093f9bfdd507c, the IuUP stack can send INIT
event more than once, it sends one each time an IuUP Initialization
message is received.
This is done since potentially a peer could send an Initialization
message at any time with a different subflow size configuration. So
ideally we should update all osmo-mgw state regarding codecs, and
forward the Init starting the procedure on the other conn of the
endpoint.
However, this scenario is most probably not going to happen right now
and it would be a lot of work to implement and test,
and subsequent INITs we received will almost surely come from
retransmissions of the initial Initialization message, which means
content will not really change.
Hence, it makes sense to simply drop the receive message (the IuUP stack
already takes care of re-ACKing it) and let the endpoint state continue
with its ongoing procedures.

Related: SYS#4705
Change-Id: Ib97bc6f57d265622e24a776b96f0a82c25d33d39
1 file changed