Add support to allow SWIF to handle copying of files to/from the job.

[mholtrop]

With SWIF, the correct way to copy files is to let SWIF handle all the I/O, so that the job slot is not used for these operations. This would also make it easier to copy output directly to tape from the job.

To do this, we need to add an option to the [Job] section to skip the cleanup step of the job. There is already an option to skip the copying out of the job. I think the job script already verifies if the files are already available and won't copy them again, but this should be checked and tested.

[baltzell]

I've seen evidence this was already done in the jobs Zhaozhong has been submitting, in that SWIF is delivering the output files.

But I wonder if the existence of those output files is being checked before reporting job success (zero exit code), since we have some cases where SWIF complains that they didn't exist. It's best to check and report non-zero exit code if output files are missing, for example, to make it more clear what went wrong and what people should do to recover.

Note, if outputs are really optional, SWIF has a directive for that.