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
```
756539f4fc