specify host/port for job.notifyURL

[bobbens]

I want to run the docker images on a machine that already is hosting web services. My idea would be to use apache proxy to forward from a subdomain to the non-standard http port of the docker. However, I found that the job.notifyURL seems to be set to https://localhost/.... Besides allowing specifying non-standard ports, it might be better to generalize this to also allow different hosts.