HPCC-8883 Allow file uploads to happen in the background

Fixes HPCC-8883

Signed-off-by: Gordon Smith <gordon.smith@lexisnexis.com>
Merge pull request #5721 from GordonSmith/HPCC-8883

HPCC-8883 Allow file uploads to happen in the background

Reviewed-By: Kevin Wang <kevin.wang@lexisnexis.com>
Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>