Bug 36882: Reapply flatpickr to cloned entry

Bug 36882: Reapply flatpickr to cloned entry

1) Add a patron attribute type:
   http://localhost:8081/cgi-bin/koha/admin/patron-attr-types.pl?op=add_attribute_type
2) Make sure its repeatable + is_date
3) Visit overdues:
   http://localhost:8081/cgi-bin/koha/circ/overdue.pl
4) Click the 'add' button under the date custom attribute
5) Click on the newly created input, notice the flatpickr pop up doesnt
   show
6) Apply patch. Repeat.

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>