Bug 30935: Holds to pull shows wrong first patron

When different patrons have item level holds on the same item, Holds to
pull shows wrong first patron.

Test plan:
1) Place a record-level hold on a biblio with an available item
2) Check the Holds to pull page (circ/pendingreserves.pl)
--> The biblio should appear in the list and the patron should appear in the 'First patron' column
3) Place a second record-level hold on the same biblio
4) Go back to the Holds to pull page
--> The biblio is still there, but the patron in the 'First patron' column is the second patron
5) Place a third record-level hold on the same biblio
6) Go back to the Holds to pull page
--> The biblio is still there, but the patron in the 'First patron' column is the third patron
7) Apply the patch
8) Go back to the Holds to pull page
--> The biblio is still there and the patron in the 'First patron' column is the first patron

Signed-off-by: Sally <sally.healey@cheshiresharedservices.gov.uk>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>

circ/pendingreserves.pl

@@ -219,6 +219,7 @@ my $holds_biblios_map = {
             {
                 join    => ['itembib', 'biblio'],
                 select  => ['me.biblionumber', 'me.reserve_id'],
+                order_by => { -desc => 'priority' }
             }
         )->unblessed
     }