core: use wrappers for DBus object registration/unregistration

When providing a service on the bus daemon and a private connection,
we'll need to track objects so we can register them with the
private connection too.  Thus all registration/unregistration
calls have to go through the NMDBusManager, not straight to
dbus-glib.

src/nm-active-connection.c

@@ -217,8 +217,7 @@ nm_active_connection_export (NMActiveConnection *self)
 
 	priv->path = g_strdup_printf (NM_DBUS_PATH "/ActiveConnection/%d", counter++);
 	dbus_mgr = nm_dbus_manager_get ();
-	dbus_g_connection_register_g_object (nm_dbus_manager_get_connection (dbus_mgr),
-	                                     priv->path, G_OBJECT (self));
+	nm_dbus_manager_register_object (dbus_mgr, priv->path, self);
 	g_object_unref (dbus_mgr);
 }