CppunitTest_sw_ooxmlimport's testFdo69636: use getShape()

getShape() doesn't case if the object is on a drawinglayer one or a
Writer TextFrame, and that's exactly what we want. (Currently is a
TextFrame, but will be a drawinglayer object when shape with text will
be imported as shape with textbox.)

Change-Id: I6ae981700d214447f326e6a0fb550b98380bc10c