hnbgw: set default RNC ID to 23 (for testing)

This should ultimately be user configurable, but for now 23 is better than 0.
diff --git a/src/hnbgw.c b/src/hnbgw.c
index 3421f4f..dab1085 100644
--- a/src/hnbgw.c
+++ b/src/hnbgw.c
@@ -404,6 +404,7 @@
 	talloc_asn1_ctx = talloc_named_const(NULL, 0, "asn1_context");
 
 	g_hnb_gw = hnb_gw_create(tall_hnb_ctx);
+	g_hnb_gw->config.rnc_id = 23;
 
 	rc = osmo_init_logging(&hnbgw_log_info);
 	if (rc < 0)