Make it possible to disable access_ip (openstack provider) (#5239)

* Add a variable do disable access_ip

* Document the use of use_access_ip

contrib/terraform/openstack/kubespray.tf

@@ -70,6 +70,7 @@ module "compute" {
   supplementary_node_groups                    = "${var.supplementary_node_groups}"
   worker_allowed_ports                         = "${var.worker_allowed_ports}"
   wait_for_floatingip                          = "${var.wait_for_floatingip}"
+  use_access_ip                                = "${var.use_access_ip}"
 
   network_id = "${module.network.router_id}"
 }