Bug 14801: Fix Reserves.t -- Follow-up for ChargeReserveFee

Bug 14801: Fix Reserves.t -- Follow-up for ChargeReserveFee

The problem making some tests fail, actually was the unneeded addition
of zero accountline records by ChargeReserveFee, called by AddReserve.
The balance is still zero, but a test like !$var responds differently
when var is 0.00 instead of 0 or undef.

This patch adjusts the test in ChargeReserveFee in order to prevent
adding these records with 0.00.
The first patch that adjusts the tests in Reserves.t is not strictly
needed anymore, but can stay.

Test plan:
[1] Run t/db_dependent/Reserves.t
[2] Run t/db_dependent/Reserves/GetReserveFee.t

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Tomas Cohen Arazi <tomascohen@unc.edu.ar>