Bug 12337 - Multi-clicking the renewal buttons on circulation.pl can trigger "renewal...

Bug 12337 - Multi-clicking the renewal buttons on circulation.pl can trigger "renewal failed" message.

Each time the "renew all" or "renew or return" buttons are click, the
renewal process is triggered. If the patron only has one renewal left,
and the button is multi-clicked, the librarian may receive a
"renewal failed" message even though the renewal did occur. In
addition, this can just unwanted multiple consecutive renewals
as well.

Test Plan:
1) Check out an item to a patron that can have 1 renewal
2) Click the "renew all" button multiple times, fast and furiously
3) Note the "renewal failed" messaged
4) Apply this patch
5) Repeat steps 1 and 2
6) Note the item is now renewed without the failure message

Signed-off-by: Nick Clemens <nick@quecheelibrary.org>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>