Bug 21008: Use patron object to get category_type

Bug 21008: Use patron object to get category_type

This patch makes borrower_add_additional_fields() in both pay.pl and
paycollect.pl use the right object to pick the category_type.

It also populates the extendedattributes template variable in pay.pl
which was missed by a change.

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>