Enable VPNaaS functional tests in the neutronclient gate
Enable VPNaaS functional tests in the neutronclient gate

This patch is enable VPNaaS functional tests in gate after
the project come back.

This is follow up the latter of [1].

[1] https://review.openstack.org/#/c/404366/

Change-Id: Idc9a021dc5916757b3698bd74866db2e7f824475

openstack/python-neutronclient,noironetworks/python-neutronclient,openstack/python-neutronclient,noironetworks/python-neutronclient