HPCC-9235 - Avoid restart distributor delays

The refactored distributor (>=3.10.0) introduced an extra small
delay (~100ms) when the distributor was wound up.
If inside a loop with relatively small amounts of records
and there were a number of them, this delay could build up and
become significant.

Signed-off-by: Jake Smith <jake.smith@lexisnexis.com>
Minor changes following review
Merge pull request #4332 from jakesmith/hashdist-loop-opt

HPCC-9235 - Avoid restart distributor delays

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>