Configure Cassandra nodes to lookup their IP address by their fully qualified domain name

[wallrj]

• Also ensure that they only ever use the Kubernetes seed provider service
• And ensure that that service publishes the seed IP addresses as soon as they are known,
• so that seeds them selves can find themselves when they are starting up.

This is a cut down version of #330

• without the headless service per statefulset, which I think may be unnecessary, since nodes only have to be able to lookup their own FQDN.
• and without the E2E tests, because I haven't yet figured out how to force minikube to change the IP address of a pod when it's recreated.

Fixes: #319

Release note:

NONE

[munnerz]

and without the E2E tests, because I haven't yet figured out how to force minikube to change the IP address of a pod when it's recreated.

When a pod is deleted, in 99% of cases it should have a new IP address. Can we make a test that deletes the pod and verifies the IP has changed? (perhaps we delete the pod again if it hasn't changed first time?).

We definitely need an e2e test for this - ideally the test would be labelled "Resiliency" too, as the first of a suite of resiliency tests.

[wallrj]

/retest

[munnerz]

/lgtm /approve

[jetstack-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: munnerz

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files: - ~~[OWNERS](https://github.com/jetstack/navigator/blob/master/OWNERS)~~ [munnerz] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment