HPCC-11775 Improve efficiency of WUiterate in Sasha

WUiterate which scans and filters archives and online workunits,
accessed Dali in an inefficient way, especially in the case of
requesting a single workunit.

Signed-off-by: Jake Smith <jake.smith@lexisnexis.com>
No, because mkDateCompare() normalizes the search item into the form:

X99999999-999999

so low and high would both be W20140101-020304 which would fail to match ayny workunits with suffixes.  (Not a new bug though.)