HPCC-9117 Stopping of dafilesrv generates odd message

Previous fix did not completely address the issue.

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>
Merge pull request #4446 from richardkchapman/dafilesrv-error

HPCC-9117 Stopping of dafilesrv generates odd message

Reviewed-by: Gavin Halliday <ghalliday@hpccsystems.com>