enable ctrl bind config for various programs

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.
diff --git a/openbsc/include/openbsc/bsc_nat.h b/openbsc/include/openbsc/bsc_nat.h
index 027b6de..309adb1 100644
--- a/openbsc/include/openbsc/bsc_nat.h
+++ b/openbsc/include/openbsc/bsc_nat.h
@@ -423,7 +423,8 @@
 void bsc_nat_send_mgcp_to_msc(struct bsc_nat *bsc_nat, struct msgb *msg);
 void bsc_nat_handle_mgcp(struct bsc_nat *bsc, struct msgb *msg);
 
-struct ctrl_handle *bsc_nat_controlif_setup(struct bsc_nat *nat, int port);
+struct ctrl_handle *bsc_nat_controlif_setup(struct bsc_nat *nat,
+					    const char *bind_addr, int port);
 void bsc_nat_ctrl_del_pending(struct bsc_cmd_list *pending);
 int bsc_nat_handle_ctrlif_msg(struct bsc_connection *bsc, struct msgb *msg);