osmo-gbproxy.cfg: fix conflict with osmo-sgsn.cfg

Listen on 127.0.0.100 by default, so there is no conflict on
127.0.0.1:23000. This allows starting both services with their default
configuration, like we are doing it in the Osmocom-Debian-install-*
jenkins jobs.

Related: OS#3369
Change-Id: I6e3053de8885a7954296d820c6a069d06276e4df
1 file changed