Code review comment for lp://staging/~pwlars/core-selftest-agent/agent-config

Actually, I don't know that I'll even need a retry queue so I took it out for now. It may be necessary to retry internally for a failed manifest download or something, but I don't think this service has a concept of an infrastructure failure outside of its control that would require requeueing. I also replaced the hostname bit with socket.gethostname()