Automatic merge from submit-queue

fix typo in kubeadm join -h

```
Flags:
      --config string                Path to kubeadm config file
      --discovery-file string        A file or url from which to load cluster information
      --discovery-token string       A token used to validate cluster information fetched from the master
      --skip-preflight-checks        skip preflight checks normally run before modifying the system
      --tls-bootstrap-token string   A token used for TLS bootstrapping
      --token string                 Use this token for both discovery-token and tls-bootstrap-token
```