Make integration test reusable

[yurishkuro]

I was looking at BaseETest.java in light of the docker-compose question https://github.com/uber/jaeger/issues/286.

It seems the test is a fairly generic end-to-end check of "is my Jaeger installation wired and working correctly" (@black-adder - didn't we have a similar one in the main repo?)

My question is - why not implement that test in the main jaeger repo, in Go, and build it as a Docker image, with some parameters controlled via env variables? Then if issue 286 results in a docker-compose file in the repo, it can be tested by adding the e2e as the last step, and k8s and openshift templates can also be tested with the same docker image.

[pavolloffay]

What we can also do is to reuse that new compose file for xdock tests. Xdock compose file would just simply extend the default docke-compose deployment (e.g. docker-compose up -f default-compose.yml -f xdock-compose.yml) and add crossdock, test_driverand xdock-langs. This way we would not have to test that new compose file separately. We did very similar thing in hawkular-apm instrumentation-framework.