[contrib/terraform/openstack] Add supplementary node groups

* Add supplementary node groups

  To add additional ansible groups to the k8s nodes, such as
  `kube-ingress` for running ingress controller pods. Empty by default.

contrib/terraform/openstack/modules/compute/variables.tf

@@ -59,3 +59,7 @@ variable "bastion_fips" {
 variable "supplementary_master_groups" {
   default = ""
 }
+
+variable "supplementary_node_groups" {
+  default = ""
+}