Adds eureka and test infrastructure to support it

[codefromthecrypt]

This adds Eureka discovery properties, and some test infrastructure so we can easily verify it from a different (test) pod.

notably the following:

• command - allows us to customize the entrypoint used to start zipkin, so that we can block on a peer container (something you can't do with initContainers)
• args - allows us to pass arguments to the command. even though we use this in tests, it is also usable normally to do things like adjust logging levels.
• extraServicePorts - allows us to expose a port inside the same pod, so that we can access it in a test pod. In this case our test eureka container, to verify zipkin registered there,