compositor: Fix weston_subsurface_is_synchronized() return value.

Commit 280e7dd918f1717c7d677676384a9cd991097741 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>
diff --git a/src/compositor.c b/src/compositor.c
index ac5bda2..ff62b5f 100644
--- a/src/compositor.c
+++ b/src/compositor.c
@@ -2639,7 +2639,7 @@
 		sub = weston_surface_to_subsurface(sub->parent);
 	}
 
-	return true;
+	return false;
 }
 
 static void