Bug 32878: (follow-up) Exclude non_priority holds

Bug 32878: (follow-up) Exclude non_priority holds

This patch filters out non_priorty holds in the on_reserve condition.

Test plan
1) Run t/db_dependant/Holds.t
2) Note it fails without this patch
3) Apply patch
4) Re-run the above test, note it now passes

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
(cherry picked from commit 042cba5db1ee7752304e2e03c9a7b239ffe88735)
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>