TemporaryJobs now honors the HELIOS_HOST_ADDRESS env var

HELIOS_HOST_ADDRESS is the IP address we should use to reach the host, instead of
the hostname. This is used when running a helios cluster inside a VM, and the containers
can be reached by IP address only, since DNS won't be able to resolve the host name of
the helios agent running in the VM.
Merge pull request #125 from spotify/rculbertson/temp-job-visible-ip

TemporaryJobs now honors the HELIOS_HOST_ADDRESS env var