tests: extract an utility method for image ids
tests: extract an utility method for image ids

warmchang/minikube,warmchang/minikube,warmchang/minikube,kubernetes/minikube,kubernetes/minikube,warmchang/minikube,warmchang/minikube,kubernetes/minikube,warmchang/minikube,kubernetes/minikube,kubernetes/minikube,kubernetes/minikube,warmchang/minikube,kubernetes/minikube