Comment 5 for bug 1694420

As pointed out in #2, a kolla-side fix would be to add the 'port_security' to the list of extension_drivers list for ML2 like in [1]. It's good practice to have this extension enabled.

[1] http://logs.openstack.org/58/466158/4/check/gate-tempest-dsvm-neutron-full-ubuntu-xenial/a2c03a6/logs/etc/neutron/plugins/ml2/ml2_conf.ini.txt.gz