kafka-test-(failover|latency)

Actually renamed now to kafka-client-experience, but repo names and docker build may lag behind.

Just some kind of framework, with some kind of metrcis, basically the sample Producer and Consumer behavior, meant to run in Kubernetes using test-kafka.yml.

Useful in two ways:

• Keep it running to detect how Kafka ops affects clients.
• Scale up and down, and/or change intervals, to see how it affects metrics.
  • see start of container logs for env var names.

Our current testing ambition is summarized in https://github.com/Yolean/kubernetes-kafka/issues/84#issuecomment-341966523