Fix deletion of non-default node groups

Fixes a bug introduced in
https://review.opendev.org/c/openstack/magnum-capi-helm/+/915031/5..6
which causes the incorrect list of node groups being processed
when the _update_helm_release method is invoked from the driver's
delete_node_group method.

Closes-bug: #2095539

Change-Id: I98e81a107162272ddbe63e30eba9db188893b8ac

magnum_capi_helm/driver.py

@@ -812,8 +812,7 @@ class Driver(driver.Driver):
             additionalStorageClasses=additional_storage_classes,
         )
 
-    def _process_node_groups(self, cluster):
-        nodegroups = cluster.nodegroups
+    def _process_node_groups(self, cluster, nodegroups):
         nodegroup_set = []
         for ng in nodegroups:
             if ng.role != NODE_GROUP_ROLE_CONTROLLER:
@@ -878,7 +877,7 @@ class Driver(driver.Driver):
                     "enabled": self._get_autoheal_enabled(cluster),
                 },
             },
-            "nodeGroups": self._process_node_groups(cluster),
+            "nodeGroups": self._process_node_groups(cluster, nodegroups),
             "addons": {
                 "openstack": {
                     "csiCinder": self._storageclass_definitions(

releasenotes/notes/fix-nodegroup-delete-c83210c6029041d2.yaml

@@ -0,0 +1,8 @@
+---
+fixes:
+  - |
+    Fixed an issue where non-default node groups could not be
+    individually deleted. The node groups would get stuck in
+    the DELETE_IN_PROGRESS state and the underlying VMs would
+    keep running. Node groups were only cleaned up when the
+    entire cluster was deleted.