LP#1287510 Add missing column to upgrade script

If you come via upgrade and not a fresh 2.5 DB, you are probably
missing the action.aged_hold_request.behind_desk column.  Add it in a
harmless way.

Signed-off-by: Dan Wells <dbw2@calvin.edu>
Signed-off-by: Ben Shum <bshum@biblio.org>