[ofono] Remove cellular service when network goes away

Otherwise services keep piling up when SIM cards are changing. Also,
they waste certain amount of space in the permanant storage and we
provide no way to the user to remove those.

connman/plugins/sailfish_ofono.c

@@ -419,12 +419,23 @@ static void modem_create_network(struct modem_data *md)
 static void modem_destroy_network(struct modem_data *md)
 {
 	if (md->network) {
+		struct connman_service *service =
+			connman_service_lookup_from_network(md->network);
+
+		if (service) {
+			connman_service_ref(service);
+		}
+
 		DBG("%s", ofono_modem_path(md->modem));
 		connman_device_remove_network(md->device, md->network);
 		if (md->network) {
 			connman_network_unref(md->network);
 			md->network = NULL;
 		}
+		if (service) {
+			__connman_service_remove(service);
+			connman_service_unref(service);
+		}
 	}
 }