Bug 14423: XSS bug in auth_subfields_structure

Bug 14423: XSS bug in auth_subfields_structure

1/ Hit a url like http://localhost:8081/cgi-bin/koha/admin/auth_subfields_structure.pl?op=add_form&authtypecode=%27%3Cscript%3Ealert%28%27oh%20noes%27%29%3C/script%3E&tagfield=%22/%3E%3Cscript%3Ealert%28%27oh%20noes%27%29%3C/script%3E
2/ Notice a ton of alert boxes pop up
3/ Apply patch
4/ Reload url, no longer get any alerts
5/ Test fuctionality still works

Signed-off-by: Jonathan Druart <jonathan.druart@koha-community.org>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>