HPCC-11252 Option on complete-uninstall to leave environment

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>
Merge pull request #5716 from richardkchapman/incomplete-uninstall

HPCC-11252 Option on complete-uninstall to leave environment

Reviewed-by: Gavin Halliday <ghalliday@hpccsystems.com>