Don't cause unnecessary resizes on containment change

When an applet is moved from a contianment to another, for a moment it was parented to the whole AppletsLayout.

since it had anchors.fill:parent set, it was resized to the whole appletslayout geometry or its max size if had any. for instance the kickoff applet would be resized to the whole screen

Reason for the change

now applet size shouldn't change anymore when draggin from on e screen to the other

Test plan

drag the kickof applet from a deskop to the one of a different screen