HPCC-11072 Add total time for roxie and hthor

The existing code calculates "Total thor time" for thor
cluster by adding all of graph times togethor. In this
fix, similar to the "Total thor time" for thor, "Total
cluster time" is calculated for both roxie and hthor.
Both "Total thor time" and "Total cluster time" are
reported inside the WsWorkunits.WUINfo response using
new name: "TotalClusterTime".

Signed-off-by: wangkx <kevin.wang@lexisnexis.com>
Might be cleaner if you set the returned values to 0 if not available?