Bug 21136: Fix add/edit patron when cities are defined

Bug 21136: Fix add/edit patron when cities are defined

Same as bug 21085.

When cities are defined, there is a select with name="select_city" added
to the DOM and its value will be passed to memberentry.pl
We must remove it from the attribute list before creating the
Koha::Patron object

No property select_city for Koha::Patron at
/usr/share/perl5/Exception/Class/Base.pm line 73

Test plan:
Define cities
Add or edit a patron, save

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>