Bug 11889: (follow-up) Remove share if you are the new owner

Bug 11889: (follow-up) Remove share if you are the new owner

This will probably be exceptional. But if the staff member already had
a share for a private list of the patron he deletes now, he will be
the new owner and we should remove the share record.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Cédric Vita <cedric.vita@dracenie.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>