Strangely, Zemke-Rhyne was associated to the webserver-legacy role.
Actually, Zemke-Rhyne is mainly used to provision secrets
to Docker containers. So it's more logic to deploy it to
the Saltmaster role, as it's an integral part of deployment.
The .ssh/authorized_keys file will be reprovisonned each time
configuration (and so data/servers.json) changes.
Ref T1412