HPCC-11958 Add Roxie State check to preflight

This fix uses the same logic as in ecl-roxie to retrieve
and format information about roxie state. The information
is displayed inside ECLwatch preflight page. WsMachine
thread pool is used to improve the performance of
retrieving the information.

Signed-off-by: wangkx <kevin.wang@lexisnexis.com>
the context parameter is missing a leading _.

I'm not 100% sure whether the member will be initialised correctly or not - possibly because of the member initialisation syntax.