HPCC-8637 - Make thorslave dali connection optional.

Only register thor slaves with Dali if configuration option
defined (Debug/@slaveDaliClient)

Signed-off-by: Jake Smith <jake.smith@lexisnexis.com>
Merge pull request #3888 from jakesmith/slavedaliclient

HPCC-8637 - Make thorslave dali connection optional.

Reviewed-By: Anthony Fishbeck <anthony.fishbeck@lexisnexis.com>
Reviewed-By: Gavin Halliday <gavin.halliday@lexisnexis.com>
Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>