This patch updates the haproxy group_vars logic to only enable
OVN-related VIPs when the OVN ML2 plugin is used. It also removes
OVN bits from the inventory to be added as an env.d override
as needed.
Change-Id: Ied1e79965c340c1d4ca430a830199978782117d0
Depends-On: https://review.openstack.org/623515