Fixes for Hetzner terraform and Hetzner Cloud (#8702)

* - add ability to specify the network_zone in hetzner terraform
- Export the network id from hetzner terraform the the generated inventory.ini

* - Add with_networks variable to allow different deployments of hcloud controller manager

- Add network id to hcloud controller secret (added via the inventory)

- Don't include extra_args if it's not set

contrib/terraform/hetzner/main.tf

@@ -10,6 +10,7 @@ module "kubernetes" {
   machines = var.machines
 
   ssh_public_keys = var.ssh_public_keys
+  network_zone = var.network_zone
 
   ssh_whitelist        = var.ssh_whitelist
   api_server_whitelist = var.api_server_whitelist
@@ -34,9 +35,9 @@ data "template_file" "inventory" {
       keys(module.kubernetes.worker_ip_addresses),
       values(module.kubernetes.worker_ip_addresses).*.public_ip,
     values(module.kubernetes.worker_ip_addresses).*.private_ip))
-
     list_master = join("\n", keys(module.kubernetes.master_ip_addresses))
     list_worker = join("\n", keys(module.kubernetes.worker_ip_addresses))
+    network_id = module.kubernetes.network_id
   }
 }