Bug 17741: Use Koha::Patron->holds when deleting a patron

Bug 17741: Use Koha::Patron->holds when deleting a patron

There is a TODO in Koha::Patron->delete, this method should call the
Koha::Patron->holds to retrieve the holds made by the patron we are
removing instead of calling Koha::Holds->search

Test plan:
  prove t/db_dependent/Koha/Patrons.t
Should return green

Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>