[cern] drop k8s requirement on .sh file

Rely purely on nova metadata to get the IP of the master VM and use that IP for all subject alt name settings. Drop requirement on getting the ip using a bash command.

Closes #4221

magnum/drivers/common/templates/kubernetes/fragments/make-cert.sh

@@ -24,12 +24,12 @@ if [ "$TLS_DISABLED" == "True" ]; then
   exit 0
 fi
 
-if [[ -z "${KUBE_NODE_PUBLIC_IP}" ]]; then
-    KUBE_NODE_PUBLIC_IP=$(curl -s http://169.254.169.254/latest/meta-data/public-ipv4)
-fi
 if [[ -z "${KUBE_NODE_IP}" ]]; then
     KUBE_NODE_IP=$(curl -s http://169.254.169.254/latest/meta-data/local-ipv4)
 fi
+KUBE_NODE_PUBLIC_IP=${KUBE_NODE_IP}
+KUBE_API_PRIVATE_ADDRESS=${KUBE_NODE_IP}
+KUBE_API_PUBLIC_ADDRESS=${KUBE_NODE_PUBLIC_IP}
 
 sans="IP:${KUBE_NODE_PUBLIC_IP},IP:${KUBE_NODE_IP}"
 if [ "${KUBE_NODE_PUBLIC_IP}" != "${KUBE_API_PUBLIC_ADDRESS}" ] \