[cloud] Stop CloudFormation module from always making changesets (#26619)

In Python a function is always truthy, and the name of the
`create_changeset` function was being accidentally used instead of
`module.params['changeset']`.

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

@@ -518,7 +518,7 @@ def main():
     if state == 'present':
         if not stack_info:
             result = create_stack(module, stack_params, cfn)
-        elif create_changeset:
+        elif module.params.get('create_changeset'):
             result = create_changeset(module, stack_params, cfn)
         else:
             result = update_stack(module, stack_params, cfn)