Instead of allowing docker-compose to rebuild it.
With this change we tag the image with a test label, and use that
in the testing as this is simpler that dealing with a dynamically
generated docker-compose file.
This change adds a docker compose configuration that's used with
the `elasticsearch.test.fixtures` plugin to start up the image
and check that the TCP ports are up.
We can build on this to add other checks for culster health,
run REST tests, etc.
We can add multiple containers and configurations to the compose
file (e.x. test different env vars) and form clusters.
Stuart Tettemer
Alpar Torok