[osmocom-analog] PBX sends PRACK during call progress which osmo-cc-sip-endpoint rejects

Hi Andreas: Thank you for this - the signalling should now work correctly, as the call connects immediately once the internal extension 221 (against which osmo-cc-sip-endpoint registers) is called. There is one issue remaining - once connected, no audio is transmitted. I don't believe this is related to this patch, though, as my Sipgate account continues working normally with the patch applied. As I am testing this in an openSUSE VM, I suspect it will be more of a firewall issue - or perhaps yet another Auerswald issue. I will be looking into this in more detail a little later today. I'm also attaching a SNGREP capture just in case this were helpful. Thank you and best regards, Markus