Allow console login to agent image

Because the agent ISO is ephemeral, it is probably safe to allow a user to log in to it with a password. If the network configuration is broken, a user may have no other way to debug it other than to log in through the console, which is currently not possible.

The best password to set would be the kubeadmin password used for the OpenShift GUI, since we'll have generated that already.

We must take care to test that this does not result in the installed nodes on disk allowing login with a password.