osmo-gbproxy-master (derived from osmo-sgsn-master)
Using a separate container will allow us to do gbproxy specific things like waiting for physical net-devices to show up in the docker netns before actually starting the osmo-gbproxy executable
Testing FR support in osmo-gbproxy is a bit more complicated as it involves the "hdlc" net-devices privded by the hdlc_fr.ko kernel module.
So we need to * run on a host with actual hdlc net-devices (e.g. dahdi_dyamic_loc) * move those net-devices into the containers after starting them * wait for the net-devices to appear in the containers before starting either gbproxy or the test suite
