Add ctrl_vty_init() calls and feed the ctrl_vty_get_bind_addr() return value to
ctrl_interface_setup() in the following programs:
osmo-bsc
osmo-bsc_nat
osmo-nitb
osmo-sgsn
For osmo-sgsn, move the control interface setup invocation below the config
parsing, so that the ctrl_vty_get_bind_addr() can return the configured
address.