Torque job failed if standard output and error files are hosted until the job is completed

[ZQyou]

This line is not sufficient to determine the job completeness if standard output and error files are hosted until the job is completed

https://github.com/eth-cscs/reframe/blob/007bc0b2b477a0ef86eeb4bb3b7eb00e4c0301ec/reframe/core/schedulers/torque.py#L95

We still need these line before return:

        with os_ext.change_dir(job.workdir):
            done = os.path.exists(job.stdout) and os.path.exists(job.stderr)