Add database directory mount for openvswitchdb
Add database directory mount for openvswitchdb

openvswitchdb creates a db.conf file in /etc/openvswitch.  This just
maps it to the host so we don't lose data.

Change-Id: Ic773ba94522f108a765a09849e2f442ef3ca3bcf

openstack/tripleo-heat-templates,openstack/tripleo-heat-templates,trozet/opnfv-tht,trozet/opnfv-tht,trozet/opnfv-tht,dprince/tripleo-heat-templates,dprince/tripleo-heat-templates