Bug 5713 :debug calculation when fines are reversed then re-payed

Bug 5713 :debug calculation when fines are reversed then re-payed

Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
I could not reproduce the calculation bug, but after
applying this patch multiple pay/reverse cycles only
are still only  2 lines in accountlines, which makes the
display a lot less confusing.
Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
(cherry picked from commit 5b945d8c415aa610e4ded830825f43bd8592d109)

Signed-off-by: Chris Nighswonger <chris.nighswonger@gmail.com>