inter-BSC Handover lacks AoIP Transport Layer Address, i.e. only works with SCCPlite
Since inter-BSC Handover support for osmo-bsc was developed on SCCPlite, it's not surprising that I forgot
to include the AoIP Transport Layer Address IE in the Handover Request Acknowledge message,
which tells the MSC the BSC's RTP address and port information.
In SCCPlite this works with a Circuit Identity Code instead, and even though we're also omitting the CIC in
the Handover Request Acknowledge message, the CIC should remain unchanged and is already known
(determined even) by the MSC. So it's fine on SCCPlite, broken on "real" A over IP.
This is also a prerequisite for testing inter-BSC Handover with osmo-msc, since osmo-msc has no SCCPlite support.
actually osmo-bsc's handover_fsm.c completely lacks the part that establishes an MSC-side MGW endpoint CI,
which is needed for AoIP. On SCCPlite that side of the MGW endpoint is done by the SCCPlite MSC.
So it needs a few more states for AoIP which I completely missed until now