HPCC-11691 Roxie can core on control:unlockdali

If there is a wu queue active, Roxie may core on a control:unlockDali call, as
the queue is cleared asynchronously.

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>
Merge pull request #6066 from richardkchapman/roxie-disconnect-core

HPCC-11691 Roxie can core on control:unlockdali

Reviewed-By: Jake Smith <jake.smith@lexisnexis.com>
Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>