container-linux: restrict ssh to sudoers and wheel
container-linux: restrict ssh to sudoers and wheel

This change adjusts permissions on the CoreOS cluster to match the
Kubernetes ABAC. Because the API server requires no authentication when
connecting over the loopback interface on the controller, it's important
to do this to avoid privilege escalation.

wuvt/wuvt-ansible,wuvt/wuvt-ansible,wuvt/wuvt-ansible,wuvt/wuvt-ansible