Add extension fields to the response on network and port create.
This patch set is based on [1] which calls for each core plugin
to apply similar logic to support extensions that rely on
extend_dict functions.
We saw the issue with CI failures after the addition of the
timestamp extension.
[1] https://review.openstack.org/#/c/276219/
Co-Authored-by: Salvatore Orlando <salv.orlando@gmail.com>
Change-Id: I15bff78610681d3ad36766138316a249efb21ae6
63a12ec964