Bug 34572: Simplify template logic around check-in input form

Bug 34572: Simplify template logic around check-in input form

This patch makes a minor simplifying change to the check-in template
around how to style the barcode input field in dropbox or fine-exempt
mode.

To test, apply the patch and go to Circulation.

- If necessary, check some items out to patrons so that you have items
  to check in.
- Go to the check-in page and click the icon inside the barcode field to
  expand the panel of options.
- Check the "book drop mode" checkbox. The barcode field should now be
  highlighted yellow.
- Check in an item. When the page redisplays, the barcode field should
  have the same highlighted style.

- If necessary, enable the finesMode system preference.
- On the check-in page, in the panel of options, check the "Forgive
  overdue fines" checkbox. Test checking in again, confirming the same
  style consistency in the barcode field.

Signed-off-by: Inkeri <inkeri.hakulinen@helsinki.fi>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
(cherry picked from commit edb9787fc85752c636e0d982871c4b715a2e57d8)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>