Improve the robustness of the deployment via a few methods:

- add retry logic for starting the master process
- shutdown existing slave services before the master service
- log an error when 'clusterrunner stop' fails
Yup, there has been a number of occasions when the Deploy job would fail, and I'd go to the console output and see something like "Master service failed to respond", and I'd ssh into the most host and wouldn't be able to find the 'clusterrunner master' process.

Now that I think about, it's possible that this was due to the jenkins process-tree killing functionality. I think it's good to keep this in here anyhow, and log anytime an attempt fails.