osmo-gsm-tester: Add osmo-mgw support
Newest master osmo-bsc is no longer compatible with osmo-bsc-mgcp, but requires osmo-mgw instead.
Support for osmo-mgw in osmo-msc is still in progress, which means osmo-msc still requires osmo-bsc-mgcp. That is, we need to run 1 instance of osmo-bsc-mgcpo controlled by osmo-msc, and 1 instance of osmo-mgw controlled by osmo-bsc. Then RTP streams are sent between those:
ms1 <-> osmo-bts <-> osmo-mgw (bsc) <-> osmo-bsc-mgcp (msc) <-> osmo-bsc-mgcp (msc) <-> osmo-mgw (bsc) <-> osmo-bts <-> ms2
Until these are added, voice tests are failing in osmo-gsm-tester.