docs: private static boolean turnOffClientInterface() {
          // we don't expect this to ever fail, but if it does, skip to dying immediately
          VoltDBInterface vdbInstance = instance();
          if (vdbInstance != null) {
              ClientInterface ci = vdbInstance.getClientInterface();
              if (ci != null) {
                  if (!ci.ceaseAllPublicFacingTrafficImmediately()) {
                      return false;
                  }
              }
          }
          return true;
      }