start jenkins using CMD

[heiderich]

I think the main purpose of the docker container is to run jenkins. So I think we should start it by default. There are other options for debugging.

[rbehrends]

I see where you are going with this, but right now it is possible to just add jenkins to the run command, e.g.

docker run -it -v jenkins_home:/var/jenkins_home -p 8080:8080 oscar-ci jenkins

This is not too onerous (and why I put jenkins in the path in the first place) and that is actually what our server script is currently doing. While the main reason why we currently type in the command manually is to test the system.

What I'd really like instead is to have two docker images (as they're based on the same initial layers, that wouldn't take up a lot more space), one of which is designed to just run Jenkins, while the other is for testing and debugging purposes. This would also mean that the server version could directly pull Jenkinsfile and the meta repo from GitHub, while the other allows for local modification.