Comment 3 for bug 2018009

Just by a quick look I think this is by design but I will confirm. Tags in neutron are handled by the tag service[1] and their are not intended to be used by mechanism drivers to pass information.

[1]
https://docs.openstack.org/neutron/ocata/devref/tag.html
https://github.com/openstack/neutron/blob/master/neutron/services/tag/tag_plugin.py