fix(api): default value for KubeVirtCluster.status.ready field

[prometherion]

What this PR does / why we need it:

It sets a default value for the KubeVirtCluster.status.ready field, suppressing the annoying values when updating for the first time KubeVirtCluster.

Which issue this PR fixes: fixes #252

Special notes for your reviewer:

Although this changes the specification, thus requiring a minor bump, the API change is absolutely minimal and could be considered a patch one.

Release notes:

NONE

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: davidvossel, prometherion

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Needs approval from an approver in each of these files: - ~~[OWNERS](https://github.com/kubernetes-sigs/cluster-api-provider-kubevirt/blob/main/OWNERS)~~ [davidvossel] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment

[davidvossel]

/ok-to-test

[maxheyer]

When do you think new versions will be released? Since this bug prevents new clusters from being created.