don't reprocess duplicate jobs

[johnsmorgan]

For ease of pipelining, it would be good if when a duplicate job is resubmitted, if an identical job already exists, mwa_client were to connect to the existing job rather than create a new one.

Use case: I start a set of jobs processing/downloading with mwa_client -c csvfile -d destdir . When those jobs are partway through processing my computer crashes. After weeding out those jobs which are completely downloaded on my machine, I would like to pick up where I left off simply by running mwa_client -c csvfile -d destdir again.

This could be default behaviour or activated by a command line flag.

It would be nice if this action were to reset the clock on the one-week expiry of the job.