KCP etcd upgrade: handle conditional update & add tests

[vincepri]

Signed-off-by: Vince Prignano [email protected]

What this PR does / why we need it:

Follow-up to #2579

• Adds a conditional check to avoid issuing an Update to the ConfigMap hasn't changed.
• Adds unit tests against UpdateEtcdMeta.

/assign @chuckha @ncdc
/cc @wfernandes
/milestone v0.3.0

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[vincepri]

Tested this on a running cluster

controllerManager:
  extraArgs:
    cloud-provider: aws
dns:
  type: CoreDNS
etcd:
  local:
    dataDir: /var/lib/etcd
    imageTag: 3.3.17-0
imageRepository: k8s.gcr.io
kind: ClusterConfiguration
kubernetesVersion: v1.16.4

got the expected result

[vincepri]

/test pull-cluster-api-test

[wfernandes]

Do we need to do a semver based check or are we just going to set it to whatever is passed in? Asking because want to know what to do for CoreDNS imageTag? 🙂
I thought we discussed something on the lines, update if it is a semver patch update.

[wfernandes]

Unless that check is happening elsewhere?

[chuckha]

that check should happen in the validating webhook so capi can reject the change as quickly as possible and not end up in an error loop that requires human intervention to fix

[vincepri]

@wfernandes @chuckha fixed all the comments, apart from the verification one, which I agree it should probably go in a validation webhook. I think for now it's probably fine do allow any kind of changes to kubeadm, we can restrict it later on

[chuckha]

/lgtm