... in ODF import, so that reference fields do not break that reference
numbering cross reference bookmarks that were corrupted by commit
679faffc.

This used to work by accident before commit
9d0c51da fixed it to actually check for
duplicates properly.

(cherry picked from commit 7c3c3006)

Change-Id: I5ed58eda7f3f2ce470a778852f6dda7a14356860
Reviewed-on: https://gerrit.libreoffice.org/19337Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>
(cherry picked from commit c5f55acd)