Bug fix for shared Pythia8/Pythia8B variable

In a recent MR, the Pythia8B member m_maxFailures was combined with the parent class Pythia8's member of the same name. However, the Pythia8 member was not moved from private to protected. Therefore, it was never initialized, so any minor Pythia error was crashing the entire production job.

Additionally, while making that change, I realized that the consecutive error count was never being reset after a successful event production, so I also made that change.