Ensure export reports progress

If a hadoop task does not either write output or reports status for 10 minutes it is killed. Make sure we check back in periodically with hadoop to ensure it doesn't kill our export processes.

@brianhw @rocha
sadly, yes...

https://github.com/spotify/luigi/blob/master/luigi/mrrunner.py#L75

Luigi hard codes the log level on slave nodes, not sure why.