elb_application_lb: when purging rules make deletion the first step (#28749)

This prevents errors when adding new rules that conflict with existing
ones that will be deleted. For example this allows adding a new rule
with the same priority of a rule that will be purged.

lib/ansible/modules/cloud/amazon/elb_application_lb.py

@@ -755,6 +755,14 @@ def create_or_update_elb_listeners(connection, module, elb):
             # Get listener based on port so we can use ARN
             looked_up_listener = get_listener(connection, module, elb['LoadBalancerArn'], listener['Port'])
 
+            # Delete rules
+            for rule in rules_to_delete:
+                try:
+                    connection.delete_rule(RuleArn=rule)
+                    listener_changed = True
+                except ClientError as e:
+                    module.fail_json(msg=e.message, exception=traceback.format_exc(), **camel_dict_to_snake_dict(e.response))
+
             # Add rules
             for rule in rules_to_add:
                 try:
@@ -774,14 +782,6 @@ def create_or_update_elb_listeners(connection, module, elb):
                 except ClientError as e:
                     module.fail_json(msg=e.message, exception=traceback.format_exc(), **camel_dict_to_snake_dict(e.response))
 
-            # Delete rules
-            for rule in rules_to_delete:
-                try:
-                    connection.delete_rule(RuleArn=rule)
-                    listener_changed = True
-                except ClientError as e:
-                    module.fail_json(msg=e.message, exception=traceback.format_exc(), **camel_dict_to_snake_dict(e.response))
-
     return listener_changed