There are several osmo processes that talk to osmo-mgw via
osmo-mgcp-client. The sample config for osmo-bsc suggest 2727 and the
sample config for osmo-msc suggests 2728 as local port default. To make
it less likely for users to get port collisions whlie setting up their
networks we should use a different port for osmo-hnbgw. Lets use 2729.