CassandraCluster node IP address changes are not currently tested

[wallrj]

#334 should solve allow C* nodes to handle changes of IP address, but we don't have E2E tests which simulate a C* node IP address changing.
Because we don't have a reliable way to replace a Pod and ensure that its replacement has a new IP address.

#330 has some code which attempted to provoke an IP address change, by running another (unrelated) pod immediately after deleting a C* pod, in the hope that the previous IP address would be consumed by the new pod and that the new C* pod would be issued a new IP address.
It doesn't work at all on minikube and it was quite flaky on kubeadm-dind-cluster.

Perhaps we can create a CNI plugin for testing which never re-uses IP addresses.

/kind bug

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