Clean up / fix osmo_bsc_filter.c
There are some leftovers from the time where osmo-bsc had an SCCPLITE/IPA based A interface. There is still an msc_con->is_connected and an msc_con->is_authenticated flag which is hard coded to 1. These flags are used by osmo_bsc_filter. Presumably the functionality in osmo_bsc_filter is presumably broken. We need to look into this and either fix it or remove it.
See also osmo_bsc_msc.c
data->msc_con->is_connected = 1;
data->msc_con->is_authenticated = 1;