HPCC-11783 Return NodeGroup in WUInfo ECLResult

The WsWorkunits/WUInfo is updated to return 'NodeGroup'
inside the ECLResult when the result has a 'logicalName'.

Signed-off-by: wangkx <kevin.wang@lexisnexis.com>
what if there's > 1 cluster using same group?

Shouldn't it return csv list of them?