A Writer image does not behave similar to other
shapes, so we need to generate a shape to get the
export code working.

Change-Id: Icfb25ceb40f73f1018d379863b836d8303e539f3
Reviewed-on: https://gerrit.libreoffice.org/65176
Tested-by: Jenkins
Reviewed-by: Tamás Zolnai <tamas.zolnai@collabora.com>