Sometimes, minikube lags behind kubernetes which can lead
to a breakage of the test suite, since minikube will fail to start
with the latest kubernetes version.
See for example [this issue](https://github.com/kubernetes/minikube/issues/4371).
This change defaults to leave the decision of which k8s version to use,
to minikube itself. This is defined in:
https://github.com/kubernetes/minikube/master/pkg/minikube/constants/constants.go
However, if one really desires it is still possible to pass
`--kubernetes-version=X.Y.Z`
to minikube initialization start command via an environment variable
before invoking the test suite:
export $MINIKUBE_ARGS="--kubernetes-version=X.Y.Z"
This allows ofcourse passing other flags to minikube also.
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