[Tags] Prevent duplicate tags in root volume of the head node.

CHANGELOG.md

@@ -12,6 +12,7 @@ CHANGELOG
 - Consider Compute fleet clean-up completed during cluster deletion when instances are either in shutting-down or terminated state.
   This is to avoid cluster deletion failure for instance types with longer termination cycles.
 - Allow cloudwatch dashboard to be enabled and alarms to be disabled in the `Monitoring` section of the cluster config.
+- Fix a bug causing duplicated tags in the head node launch template.
 
 **CHANGES**
 - Upgrade Cinc Client to version to 18.4.12 from 18.2.7.

cli/src/pcluster/templates/cluster_stack.py

@@ -87,6 +87,7 @@
     apply_permissions_boundary,
     convert_deletion_policy,
     create_hash_suffix,
+    dict_to_cfn_tags,
     get_cloud_watch_logs_policy_statement,
     get_cloud_watch_logs_retention_days,
     get_common_user_data_env,
@@ -1240,7 +1241,12 @@ def _add_head_node(self):
                 tag_specifications=[
                     ec2.CfnLaunchTemplate.TagSpecificationProperty(
                         resource_type="volume",
-                        tags=get_default_volume_tags(self._stack_name, "HeadNode") + get_custom_tags(self.config),
+                        tags=dict_to_cfn_tags(
+                            {
+                                **get_default_volume_tags(self._stack_name, "HeadNode", raw_dict=True),
+                                **get_custom_tags(self.config, raw_dict=True),
+                            }
+                        ),
                     ),
                 ],
             ),