Initially we were loading every potential upstream address into Envoy
and then routing traffic to the logical upstream service. The downside
of this behavior is that traffic meant to go to a specific instance
would be load balanced across ALL instances.
Traffic to specific instance IPs should be forwarded to the original
destination and if it's a destination in the mesh then we should ensure
the appropriate certificates are used.
This PR makes transparent proxying a Kubernetes-only feature for now
since support for other environments requires generating virtual IPs,
and Consul does not do that at the moment.
