controller loop removes service account token secrets that have not been used
  in the time specified by `--legacy-service-account-token-clean-up-period` (defaulting
  to one year), **and are** referenced from the `.secrets` list of a ServiceAccount

- kubeadm: Added better handling of errors during unmount when calling `kubeadm reset`. When failing to unmount directories under `/var/run/kubelet`, kubeadm will now throw an error instead of showing a warning and continuing to clean up said directory. In such situations, it is better for you to inspect the problem and resolve it manually. Then, you can call `kubeadm reset` again to complete the cleanup.

credentials have not been used in the time specified by `--legacy-service-account-token-clean-up-period` (defaulting to one year), **and** are referenced from the `.secrets` list of a ServiceAccount object, **and**  are not referenced from pods. This label causes the authentication layer to reject use of the credentials. After being labeled as invalid, if the time specified by `--legacy-service-account-token-clean-up-period` (defaulting to one year) passes without the credential being used, the secret...