Integration test for the tunnel code

From a unit test start kas, agent and make a few requests to Kubernetes through the proxy. Exercise both agentk->kas and kas->agentk connectivity. Ideally run multiple kas and agent replicas. Ideally we need to test both scenarios: where kas/agent route via in-memory connection and over the network.

We need to develop some test harness that allows to easily start things up in different configurations.

This is an integration test. It should use a real Redis and a real Kubernetes. We need to see how to deploy multiple agents into the cluster so that they can use in-cluster discovery for kas->agentk routing scenario.