Cannot get lock_passwd to work

Hi

I'm trying following config:

```
#cloud-config

  users:
    - name: "kairos"
      passwd: "samplepassword"
      lock_passwd: true
      ssh_authorized_keys:
        - github:zewelor
 ```

And it allows me to login, from reading code I assume it should set password hash as "!" in /etc/shadow ? There is still normal password hash there.