HPCC-8539 Add configuration option to specify dali client MP port range

For clients that use the 'default' port range of 7101-7500, read it from the
environment.xml file (if found).

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>
Merge pull request #4141 from richardkchapman/mp-ports

HPCC-8539 Add configuration option to specify dali client MP port range

Reviewed-by: Gavin Halliday <ghalliday@hpccsystems.com>