Use 'k8s.gcr.io' instead of 'gcr.io/google-containers' (#5709)

Ref: kubernetes/kubeadm/issues/2051

See: https://groups.google.com/forum/?utm_medium=email&utm_source=footer#!msg/kubernetes-sig-release/ew-k9PEBckQ/T7dFepHdCAAJ



Signed-off-by: Nguyen Hai Truong <truongnh@vn.fujitsu.com>