Capture hostname in Spark start method (resolves #1007)
Capture hostname in Spark start method (resolves #1007)

Moves the hostname capture to the start method of the Spark service job. This
resolves the issue where the hostname of the node starting the service was
being captured, thus causing the wrong IP address to be returned for the
Spark cluster leader.

BD2KGenomics/slugflow,BD2KGenomics/slugflow