HPCC-11654 Regression Test Engine generates error message at exit in
Overnight Build & Test system

Fix I/O operation error on closed file.

Signed-off-by: Attila Vamos <attila.vamos@gmail.com>
Merge pull request #6109 from AttilaVamos/HPCC-11654-fix

HPCC-11654 Regression Test Engine generates error message at exit in Overnight Build & Test system

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>