Fix missing cursor when DraggableElement handle is seperate
Fix missing cursor when DraggableElement handle is seperate

I noticed this while scrolling the demos page. When the entire element
is the handle it works. But when the handle is a separate element it
doesn't have the …-widget class. The cursor is missing because of
this.

Change-Id: I2d4d2cb66b4d563e80408fe5ab1b8a284427ae77

wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui