Bug 8228 - metadata service fix made cleaner

Bug 8228 - metadata service fix made cleaner

This patch sticks more to the architecture.

In OPNFV scenarios, Openstack metadata service may be reached
via DHCP port which acts as a GW to metadata server. VMs have
a route configured to metadata server via DHCP port.

Metadata IP and port are specified in blueprint cfg file and
processed by neutron-mapper bundle. An ip-prefix  endpoint is
registered by neutron-mapper, it points to the same mac- address
endpoint as DHCP ip-prefix endpoint, i.e. DHCP ip-prefix EP &
Metadata ip-prefix EP point to the same mac address endpoint.

This configuration is supported by VPP renderer's implementation
of location resolver. In this case both DHCP and Metadata have
the same absolute location.

When ACL manager recongnizes this fact, it will build ACL for
both endpoints behind the same interface.

Remote IP prefix is revisioned here too. Remote IP prefix is
mapped to GBP as external ip-prefix endpoint. Location resolver
then looks for external interfaces and on nodes and create a
relative location for this endpoint.

Change-Id: Id72d5646fbd7af1a8094749e58ba714bb3d84959
Signed-off-by: Tomas Cechvala <tcechval@cisco.com>