Bug 18936: (follow-up) Add missing circulation rule to fix tests

Bug 18936: (follow-up) Add missing circulation rule to fix tests

The tests passed before by a chance because the default kohadevbox
installation script added a issuing rule that had lengthunit =
days. If you use a Koha version before the commits introduced by Bug
18936 you can reproduce the Fees.t tests failing by deleting all the
issuing rules from database with

> delete issuingrules;

and then running

$ prove t/db_dependent/Koha/Charges/Fees.t

Signed-off-by: Minna Kivinen <minna.kivinen@hamk.fi>
Signed-off-by: Joonas Kylmälä <joonas.kylmala@helsinki.fi>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>