overlay elements flicker upon creation

[vaf-hub]

We use displayOverlay() to show different overlays (e.g. search(Ctrl+F) in the desktop client: or the notification overlay). When the actual element is attached to the dom it flickers. This is because it is displayed in its final state briefly before the createAnimation is called (which might for example move it in from outside the screen).

We should fix how animations work in such cases. It might be that we have similar problems in other places.