platform: refactor marking cloned routes in platform

We handle cloned routes (that have rtm_flags RTM_F_CLONED) differently.
We used to mark such routes by hacking NMIPConfigSource to have a special
value. No longer do this, because it mixes different concepts.

Note that the rt_cloned filed fits into a hole in the aligment
of NMPlatformIPRoute. Thus there is almost no overhead to this
change.

src/platform/nmp-object.c

@@ -915,12 +915,12 @@ _vt_cmd_obj_is_alive_ipx_route (const NMPObject *obj)
 	 *
 	 * If nmp_object_from_nl() would just return NULL, we couldn't look
 	 * into the cache to see if it contains a route that now disappears
-	 * (because it is cloned).
+	 * (because it changed to be cloned).
 	 *
 	 * Instead we create a dead object, and nmp_cache_update_netlink()
 	 * will remove the old version of the update.
 	 **/
-	return obj->object.ifindex > 0 && (obj->ip_route.rt_source != _NM_IP_CONFIG_SOURCE_RTM_F_CLONED);
+	return obj->object.ifindex > 0 && !obj->ip_route.rt_cloned;
 }
 
 gboolean