HPCC-8735 - Avoid seperate call to fetch total # workunits

ws_workunits, called numWorkUnitsFiltered and getWorkUnitsSorted
when requesting workunits. The latter was able to calculate the
total with minor modification and avoid the need for a seperate
pass with numWorkUnitsFiltered

Signed-off-by: Jake Smith <jake.smith@lexisnexis.com>
Add results of postfilter to cache.

Avoid re-performing postfilter when reusing cached result.

Signed-off-by: Jake Smith <jake.smith@lexisnexis.com>
Cache and reuse postfilter

Signed-off-by: Jake Smith <jake.smith@lexisnexis.com>
Merge pull request #3979 from jakesmith/hpcc-8735

HPCC-8735 - Avoid seperate call to fetch total # workunits

Reviewed-By: Gavin Halliday <gavin.halliday@lexisnexis.com>
Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>