message: snapshotter: don't use json formatter of logrus
  When using json formatter, timestamp and log level is put somewhere
  out of order. Besides, log level is not colored. So it is hard to
  find error messages from a pile of lines.
diff: @@ -19,8 +19,9 @@ func SetUp(logLevel string) error {
  return err
  }
  logrus.SetLevel(lvl)
  - logrus.SetFormatter(&logrus.JSONFormatter{
  + logrus.SetFormatter(&logrus.TextFormatter{
  TimestampFormat: log.RFC3339NanoFixed,
  + FullTimestamp: true,
  })
  return nil
  }
  