Either the document has attributes in the old namespace or in the
new, both will be imported. But export is still in the old
namespace.

Change-Id: I9f4d1ca0d8af37c13b513f99cc7d254c68867bb2
Reviewed-on: https://gerrit.libreoffice.org/59405Reviewed-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>
Tested-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>