* Bug: In cumulus/plugins.chip.powerplane.Builder._connectHTree(),
    when building the stacked VIAs over the corona Pin and the
    root buffer RoutingPad, pass the GaugeConf.HAccess flag so the
    stack stops at METAL4 (top horizontal layer).
      Before we where also adding a VIA up to METAL5 which was unused
    and caused a minimal area violation.