Bug 15135: Remove Warning Subroutine HasOverdues redefined

Bug 15135: Remove Warning Subroutine HasOverdues redefined

In staff client, while displying patron related pages (e.g. moremember.pl) you get a warning like:
moremember.pl: Subroutine HasOverdues redefined at /usr/share/kohaclone/Koha/Template/Plugin/Borrowers.pm line 52.
This occurs with all pages that have [% USE Borrowers %] in their templates (directly or via members-toolbar.inc)

To test:
- Go to Home > Patrons > Patron details for....
- Search for warning above in log
- Apply patch
- Verify that no more warnings appear
- Verify that patron pages behave as before

(Solution as of comment #18)

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Verified that warning disappears with this patch.

Signed-off-by: Jacek Ablewicz <abl@biblos.pk.edu.pl>
Signed-off-by: Brendan A Gallagher <brendan@bywatersolutions.com>
(cherry picked from commit 560bc790db6d3f8f2ff6b4e70db148445ff645e4)
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>