[baremetal] public gateway setup on prx nodes

[baremetal] public gateway setup on prx nodes

- prx: add route for public traffic to public interface
- prx: add route towards salt master through maas
- remove dashboard class from proxy node (already implements horizon)
- remove dashboard (and benchmark) class definitions (no longer used)
- (temporary) backport Pharos change for adapter template

JIRA: FUEL-305

Change-Id: Ia14a18ac0123c1134d8d99dc43da9a1f770001d0
Signed-off-by: Guillermo Herrero <guillermo.herrero@enea.com>
(cherry picked from commit 07f4e0238646fcb77072769feb8a0b68df52caca)