Prevent infinite loop from `panel:SetDragParent` (#2058)
* Prevent infinite loop from `panel:SetDragParent`
* Prevent DND infinite loop from `panel:DragMousePress`
* Remove DND infinite loop prevention from `panel:SetDragParent`
* Remove early return in `p:DraMousePress`
This will allow the rest of the method to run even if the drag parent is the panel itself