[cassandra] create etcd / controlplane servers

A good practice for production kubernetes clusters is to separate etcd and controlplane services from the worker nodes.

In our case it will also allow to have homogenous worker nodes and put the kubernetes overhead outside the cassandra servers by themselves.

Spec: 3 vms with 4 vcpus and 8Go each, default disks

---

Migrated from T4379 (view on Phabricator)