ifcfg-rh: don't chain up after failure of replace_and_commit()

If replace_and_commit() found existing route files (and the callback
has potentially already been invoked), it is wrong to chain up to
parent class and continue the update.

Fixes: f79d62692e

src/settings/plugins/ifcfg-rh/nm-ifcfg-connection.c

@@ -369,6 +369,7 @@ replace_and_commit (NMSettingsConnection *connection,
 			callback (connection, error, user_data);
 			g_clear_error (&error);
 		}
+		return;
 	}
 
 	NM_SETTINGS_CONNECTION_CLASS (nm_ifcfg_connection_parent_class)->replace_and_commit (connection, new_connection, callback, user_data);