Fix kubeadm master config hostname

Author: deitch

config/default/machine_configs.yaml

@@ -133,7 +133,7 @@ items:
       advertiseAddress: ${PUBLICIP}
       bindPort: ${PORT}
     nodeRegistration:
-      name: ${PUBLICIP}
+      name: ${HOSTNAME}
     ---
     apiVersion: kubeadm.k8s.io/v1beta1
     kind: ClusterConfiguration