HPCC-11494 Roxie dali notification issues

Backport some changes from candidate-5.0.0 made in connection with HPCC-11253,
to avoid multiple reloads on parallel threads when notifications received fro
packagemap updates.

Also contains the fixes for HPCC-11293 (delayed unload of slave queries).

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>
HPCC-11494 Roxie dali notification issues

Avoid reloading unchanged packageMaps

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>
Merge pull request #5933 from richardkchapman/roxie-notifications-2

HPCC-11494 Roxie dali notification issues

Reviewed-By: Gavin Halliday <gavin.halliday@lexisnexis.com>
Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>