Bug 31313: (QA follow-up) Show status "On hold" correctly if there are waiting holds

Bug 31313: (QA follow-up) Show status "On hold" correctly if there are waiting holds

The patch "Bug 31313: Fix availability - OPAC
opac-detail" (70cb4e22c07) cause the OPAC detail page only show
"Available" status even when there were waiting holds.

The onhold item field is removed at the same go as it was confusing
and unused since "Bug 2655: Fixes availabilty counts if items are on
hold shelf. Patch (2/2)" (a37545eb1)

Signed-off-by: Joonas Kylmälä <joonas.kylmala@iki.fi>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>