fail on invalid RTP address from MGW

When the CRCX OK returns an invalid RTP address, abort the call; fixes
MSC_Tests.TC_invalid_mgcp_crash.

The original crash happened when adding this error handling without this commit
I08c03946605aa12e0a5ce8b3c773704ef5327a7a ("fsm: use deferred deallocation" for
osmo-mgw I7df2e9202b04e7ca7366bb0a8ec53cf3bb14faf3 "fix use-after-free: require
new fsm deferred dealloc, check for term"). With this error handling added,
even though avoiding a crash, the test does not pass yet, because instead of
rejecting the call, it currently composes an Assignment Command without a
Transport Layer Address. Fix that.

Change-Id: I00c3b5ff74c05bcc2b7c39375c33419916a57193
1 file changed