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/src/osmo-bsc_nat/bsc_nat_ctrl.c b/openbsc/src/osmo-bsc_nat/bsc_nat_ctrl.c
index f3ca924..ec4243e 100644
--- a/openbsc/src/osmo-bsc_nat/bsc_nat_ctrl.c
+++ b/openbsc/src/osmo-bsc_nat/bsc_nat_ctrl.c
@@ -470,13 +470,14 @@
 	return CTRL_CMD_ERROR;
 }
 
-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)
 {
 	struct ctrl_handle *ctrl;
 	int rc;
 
 
-	ctrl = bsc_controlif_setup(NULL, OSMO_CTRL_PORT_BSC_NAT);
+	ctrl = bsc_controlif_setup(NULL, bind_addr, OSMO_CTRL_PORT_BSC_NAT);
 	if (!ctrl) {
 		fprintf(stderr, "Failed to initialize the control interface. Exiting.\n");
 		return NULL;