HPCC-11607 Core processing control:reload

Unprotected access to allQueryPackages could core if processing two reloads at
once.

It's generally a bad idea to process two at once anyway - I will be releasing
a separate commit to try to address that shortly.

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>
HPCC-11607 Core processing control:reload

Prevent multiple parallel reloads from occurring.

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>
Merge pull request #6004 from richardkchapman/roxie-reload-core

HPCC-11607 Roxie reload core

Reviewed-by: Gavin Halliday <ghalliday@hpccsystems.com>