Reconfigure dnspath to a standard directory

named/data is not strandard, let's switch to the application directory,
(bind9 for the backend used) (designate also support pdns).

https://github.com/openstack/designate/blob/master/etc/designate/designate.conf.sample#L12

Change-Id: I7229295c8282cf6b03e18cdebafa3de83b61b784