Bug 37523: CSRF error when modifying an existing patron record

Bug 37523: CSRF error when modifying an existing patron record

This patch modifies the patron entry template to avoid a CSRF error when
clicking the "Edit existing record" button after a duplicate patron is
found. The operation should be GET and thus can be a link.

To test, apply the patch and go to Patrons.

- If you aren't using the default testing data you should first locate
  an existing patron record so you can refer to the details.
- Start the process of creating a new patron record.
- Use the existing patron's data to fill out the form.
  - With the default data you can use:
    - Surname: Bennett
    - First name: Pamela
    - Date of birth: 09/16/1946
    - Any random new card number
- When you click "Save" you should get a duplicate patron warning:
  "Duplicate patron record?"
  - Click "It is a duplicate. Edit existing record."
  - You should be taken to the edit form for the existing patron.

Sponsored-by: Athens County Public Libraries
Signed-off-by: Roman Dolny <roman.dolny@jezuici.pl>
Signed-off-by: Johanna Räisä <johanna.raisa@gmail.com>
Signed-off-by: Emily Lamancusa <emily.lamancusa@montgomerycountymd.gov>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>