Bug 22111: Format amount shown on place holds when maxoutstanding is reached (staff)

Bug 22111: Format amount shown on place holds when maxoutstanding is reached (staff)

Displays amount outstanding correctly when holds are blocked
by maxoutstanding.

To test:
- Check maxoutstanding system preference value
- Add a fine to a patron account exceeding maxoutstanding
- Try to place a hold for this patron from staff
- Verify this message is shown:

     Patron has outstanding fines: 6.00

- Toggle CurrencyFormat system preference and verify display
  changes according to setting

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Mikael Olangcay Brisebois <mikael.olangcay-brisebois@inlibro.com>
Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>