Bug 10917: allow staff to update hold pickup location without modify_holds_priority

A librarian cannot modify a hold's pickup location unless he or she has
the permission modify_holds_priority. This appears to be a bug and not
by design. The reason the update fails is due to the priority not being
passed to ModReserve. The priority is not displayed when a librarian
does not have the modify_holds_priority permission.

Test Plan:
1) Remove the modify_holds_priority from your logged in user
   * User cannot be a superlibrarian
2) Attempt to change the pickup location for a hold
3) Note the change fails
4) Apply this patch
5) Repeat step 2
6) Note the change succeeds

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Template change only.
Passes all tests and QA script.

Tested:
- Confirmed that changing the pickup location is not
  possible in master without the modify_holds_priority
  permission
- Confirmed that the patch fixes the problem - pickup
  location can now be changed with and without the
  permission
- Pickup location can still not be changed, when
  IndependentBranches is activated

Signed-off-by: Galen Charlton <gmc@esilibrary.com>