Return the right radius to start reorder when dragging a Widget

Currently the radius is only one cell but in the case of a widget
we want the radius of the whole widget.

Fix: 255421400
Test: this case only happens when dagging comming from outside of the cell layuot in the corners dragging a widget
Change-Id: I3fe294d18283dbecb27df1a2d4748dd44db9b956