Update the list of log files to monitor.

def update_log_filenames(self):
        """Update the list of log files to monitor."""
        log_filenames = os.listdir(self.logs_dir)

        for log_filename in log_filenames:
            full_path = os.path.join(self.logs_dir, log_filename)
            if full_path not in self.log_filenames:
                self.log_filenames.add(full_path)
                self.closed_file_infos.append(
                    LogFileInfo(
                        filename=full_path,
                        size_when_last_opened=0,
                        file_position=0,
                        file_handle=None))
                logger.info("Beginning to track file {}".format(log_filename))