RTFSdrImport::resolve() is called for \picprop and creates an XShape
that is stored in RTFSdrImport::m_xShape and also
DomainMapper_Impl::m_aPendingShapes;
later RTFDocumentImpl::resolvePict() completely ignores that XShape
and creates a new one, which is also inserted in the document;
the first XShape is effectively leaked.

Try to avoid that by re-using the exising m_xShape in resolvePict().
Not sure if there are any problems with doing this, it's all a bit
confusing.

Change-Id: I98456242acb0766f547eb8f7d877f51d53323f3a
(cherry picked from commit ba9b63d8)