docs: protected synchronized void releaseBroker(PersistenceBroker broker)
      {
          /*
          arminw:
          only close the broker instance if we get
          it from the PBF, do nothing if we obtain it from
          PBThreadMapping
          */
          if (broker != null && _needsClose)
          {
              _needsClose = false;
              broker.close();
          }
      }