wayland: Only use async configured position if actually changed

When (un)maximizing, (un)fullscreening, the move/resize action is flagged with 'ACTION_MOVE', while e.g. 'appears-focus' does not.

When a client misbehaved and didn't immediately reply to a configure request with a commit with the corresponding ack_configure, the following commit would trigger a oddly timed move, making the window appear to move back to a previous position.

Avoid this issue by only carrying over the target window position if the configuration actually contained a new position.