HPCC-9795 Roxie needs to figure out numChannels

Some hidden attributes that were calcluated by configmgr were not in the xsd,
or were marked as readonly there. configmgr no longer calculates them, making
it very hard to set up a new Roxie cluuster.

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>
HPCC-9771 Configmgr - crashes when deleting 'null' roxie server

  - remove 'null' servers from new instances

Signed-off-by: Gleb Aronsky <gleb.aronsky@lexisnexis.com>
Community Edition 4.0.0-6 Gold

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>