Bug 24952: Add id to refund modals confirm buttons

Bug 24952: Add id to refund modals confirm buttons

This patch adds an ID to the refund confirmation modals for both
borrower account and point of sale register details pages.

Test plan:
1/ Apply patch
2/ Attempt to issue a refund to a patron
3/ Inspect the page and note the presence of an ID for the confirm
   button,
4/ Attempt to issue a refund via point of sale register details page
5/ Inspect the page and note the presence of an ID for the confirm
   button.
6/ Signoff

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>