Bug 36797: Change WHILE loop into FOREACH

Bug 36797: Change WHILE loop into FOREACH

To test:
1. Find a record that has 1000 non-waiting holds with different priorities.
2. Try loading the reserve page for that record ( /reserve/request.pl?biblionumber=X )
3. Error: Template process failed: undef error - WHILE loop terminated (> 1000 iterations)
4. APPLY PATCH
5. Try again, this time the page should load.
6. Try testing on a record with less than 1000 holds, making sure the priorities are still set right.
7. Make sure you can change your priorities and everything works right.

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>