Bug 29664: Do not show voided payments in cash_register_stats.pl

Bug 29664: Do not show voided payments in cash_register_stats.pl

Test Plan:
1) Set up your cash register
2) Take a payment
3) Void that payment
4) Verify the voided fee shows for the "All payments to the library" and
   "Payment" transaction type filters
5) Apply this patch
6) Restart all the things!
7) Verify the voided fee no longer shows for the "All payments to the library" and
   "Payment" transaction type filters

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>