osmo-hnbgw: make sure osmo_ss7_init() executed successfully

Change-Id: Ia9ecf903e79b282aa4fa88a291424681d0fe9d89
Fixes: CID#206089
diff --git a/src/hnbgw.c b/src/hnbgw.c
index 0db04af..70ee25b 100644
--- a/src/hnbgw.c
+++ b/src/hnbgw.c
@@ -536,7 +536,11 @@
 	if (rc < 0)
 		exit(1);
 
-	osmo_ss7_init();
+	rc = osmo_ss7_init();
+	if (rc < 0) {
+		LOGP(DMAIN, LOGL_FATAL, "osmo_ss7_init() failed with rc=%d\n", rc);
+		exit(1);
+	}
 
 	vty_info.copyright = osmo_hnbgw_copyright;
 	vty_init(&vty_info);