Bug 28972: Add missing foreign key constraints to holds queue table

Bug 28972: Add missing foreign key constraints to holds queue table

The table tmp_holdsqueue is missing a couple key constraints that should
be there, one for biblio and one for borrowers.

Test Plan:
1) "SHOW CREATE TABLE tmp_holdsqueue;" should show no FKs for biblio or borrowers
2) Apply this patch
3) Run updatedatabase.pl
4) "SHOW CREATE TABLE tmp_holdsqueue;" should now show FKs for biblio or borrowers

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Joonas Kylmälä <joonas.kylmala@iki.fi>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>