~koalinux/charms/trusty/neutron-contrail/vhost-phy

  Use vhost-interface instead of vhost-phy to define the local interface.
  vhost-phy is defined in dpdk installations but referenced always in vrouter_ctx,
  producing tracebacks like the one blelow in case you don't use dpdk:
  
  2017-11-02 09:45:46 DEBUG upgrade-charm Traceback (most recent call last):
  2017-11-02 09:45:46 DEBUG upgrade-charm   File "/var/lib/juju/agents/unit-neutron-contrail-0/charm/hooks/upgrade-charm", line 463, in <module>
  2017-11-02 09:45:46 DEBUG upgrade-charm     main()
  2017-11-02 09:45:46 DEBUG upgrade-charm   File "/var/lib/juju/agents/unit-neutron-contrail-0/charm/hooks/upgrade-charm", line 444, in main
  2017-11-02 09:45:46 DEBUG upgrade-charm     hooks.execute(sys.argv)
  2017-11-02 09:45:46 DEBUG upgrade-charm   File "/var/lib/juju/agents/unit-neutron-contrail-0/charm/hooks/charmhelpers/core/hookenv.py", line 715, in execute
  2017-11-02 09:45:46 DEBUG upgrade-charm     self._hooks[hook_name]()
  2017-11-02 09:45:46 DEBUG upgrade-charm   File "/var/lib/juju/agents/unit-neutron-contrail-0/charm/hooks/upgrade-charm", line 450, in upgrade_charm
  2017-11-02 09:45:46 DEBUG upgrade-charm     write_vrouter_config()
  2017-11-02 09:45:46 DEBUG upgrade-charm   File "/var/lib/juju/agents/unit-neutron-contrail-0/charm/hooks/neutron_contrail_utils.py", line 548, in write_vrouter_config
  2017-11-02 09:45:46 DEBUG upgrade-charm     ctx.update(vrouter_ctx())
  2017-11-02 09:45:46 DEBUG upgrade-charm   File "/var/lib/juju/agents/unit-neutron-contrail-0/charm/hooks/neutron_contrail_utils.py", line 510, in vrouter_ctx
  2017-11-02 09:45:46 DEBUG upgrade-charm     "vhost_physical": config["vhost-phy"] }
  2017-11-02 09:45:46 DEBUG upgrade-charm KeyError: 'vhost-phy'