compositor: Fix weston_subsurface_is_synchronized() return value.

Commit 280e7dd918 introduced a bug in the
return value of weston_subsurface_is_synchronized().

Signed-off-by: Carlos Olmedo Escobar <carlos.olmedo.e@gmail.com>
Reviewed-by: Derek Foreman <derekf@osg.samsung.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>

src/compositor.c

@@ -2639,7 +2639,7 @@ weston_subsurface_is_synchronized(struct weston_subsurface *sub)
 		sub = weston_surface_to_subsurface(sub->parent);
 	}
 
-	return true;
+	return false;
 }
 
 static void