OsmoBSC doesn't perform MGCP DLCX in all cases of channel release
Whenever we performed CRCX on one or multiple MGCP connections on osmo-mgw, we must also call DLCX to clean up.
There are situations like at least the one seen in the attached PCAP file in which CRCX+MDCX are called, but the media gateway never sees a DLCX.
I've seen this cause follow-on problems if more connections are allocated on the same endpoint, at which the mgw will refues as only two connections are permitted by endpoint.
We should have a state machine that ensures whever the SCCP connection is closed, and that SCCP connection had MGCP connections, that those MGCP connections are deleted.