HPCC-10732 Call sendRoxieControlAllNodes() to send control:querystats

The --lock flag is needed when sending control:querystats to get
correct Accumulated Counts. Inside the sendRoxieControlAllNodes(), the
sendRoxieControlLock() is called to set the flag. I also revised the
xpath for reading xgmml based on the data structure returned from
roxie.

Signed-off-by: Kevin Wang kevin.wang@lexisnexis.com