Feature #2260: "next generation" osmo-bsc_mgcp
osmo-mgcp-gw: dynamic "BTS" addresses
The VTY config has the "mgcp" / "bts ip A.B.C.D" config item.
This forces to use a fixed, single cell (BTS or RNC).
When RTP arrives from a different IP, errors occur:
<000b> mgcp_network.c:871 rtp_data_bts: Data from wrong bts 10.23.24.27 on 0x8
Make it so that we don't need to configure a fixed BTS IP.
(maybe it's already there and just a matter of config?)