HPCC-8792 - Log disk space at thor startup

Useful because in the event of disk full events, it is useful
to see the disk space before Thor clears all the temp files,
that may well have cause the disk to be full in the first place

Signed-off-by: Jake Smith <jake.smith@lexisnexis.com>
Merge pull request #4143 from jakesmith/hpcc-8792

HPCC-8792 - Log disk space at thor startup

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>