core: ignore default routes when creating configuration for generic interface

NM handles the default routes, so they shouldn't show up in the NMIP4Config
for any interface.  They get exposed via the 'default' and 'default6' properties
of the ActiveConnection instead.

src/nm-ip4-config.c

@@ -129,6 +129,12 @@ nm_ip4_config_new_for_interface (int ifindex)
 	routes_array = nm_platform_ip4_route_get_all (ifindex);
 	routes = (NMPlatformIP4Route *)routes_array->data;
 	for (i = 0; i < routes_array->len; i++) {
+		/* Default route ignored; it's handled internally by NM and not
+		 * tracked in the device's IP config.
+		 */
+		if (routes[i].plen == 0)
+			continue;
+
 		route = nm_ip4_route_new ();
 		nm_ip4_route_set_dest (route, routes[i].network);
 		nm_ip4_route_set_prefix (route, routes[i].plen);