This fixes two issues that seem to have been introduced by 98dc342:
* During drag, CSD windows being offset from their original location and
the frames rendered around them.
* Windows on additional monitors being positioned incorrectly when
dragged.
This seems to work well in floating mode with `OutputBound` workspaces.
With `Global` workspaces it seems position of dragged windows on
additional monitors isn't right before or after this...