Without the added `return {}`, calling route53.list_tags_for_resource
when called with a ResourceId of a resource without any tags would
result in the error:
jinja2.exceptions.UndefinedError: 'None' has no attribute 'items'
Because the LIST_TAGS_FOR_RESOURCE_RESPONSE was given None instead of
empty dict.
This now allows list_tags_for_resource to be called without issue on
tag-less resources.
35507f33df