// of this period, it becomes the LastKnownGood. Note that if Spec.ConfigSource is
  // reset to nil (use local defaults), the LastKnownGood is also immediately reset to nil,
  // because the local default config is always assumed good.
  // You should not make assumptions about the node's method of determining config stability
  // and correctness, as this may change or become configurable in the future.
  // +optional