Bug 27808: (QA follow-up) Make sure the update catches the items we want

Bug 27808: (QA follow-up) Make sure the update catches the items we want

This query:

SELECT *
FROM items
LEFT JOIN issues
ON issues.itemnumber=items.itemnumber
WHERE items.onloan IS NULL;

returns 961 rows on the sample data, with 2 items checked out and onloan
set to NULL.

With this tweak, the query only matches the 2 checkout items with onloan
set to NULL:

SELECT *
FROM items
LEFT JOIN issues
ON issues.itemnumber=items.itemnumber
WHERE items.onloan IS NULL AND issues.issue_id IS NOT NULL;

This is the query that needs to be used on the atomic update for
filtering the items to be updated.

This patch does that.

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
(cherry picked from commit 8df3e02885f94ef8a6f960f693c398b6646daf09)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>