re #8505: Relax the tolerance for the system test

I do not want to change the systemtest, but, because it now uses the
EventMode data, instead of using the histogram, small changes can occur.
I have changed the tolerance to require that the difference between the
current data and the result of the reduction using the event mode data
can not be greater than 1%.
Merge remote-tracking branch 'origin/feature/8505_event_mode'