Bug 15832 - Fix filter and items split-up in pendingreserves.tt

Bug 15832 - Fix filter and items split-up in pendingreserves.tt

Test plan:

- Go to circ/pendingreserves.pl (Ensure that there are biblios with many
  items on different branches),
- Check the libraries filter at the bottom of datatable. There should be
  duplicates.
- Apply this patch and return to circ/pendingreserves.pl,
- check that libraries filter should not contain duplicate,
- check that the filter works.

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Brendan Gallagher <bredan@bywatersolutions.com>