HPCC-9773 Change group variable from $user to $group in chown.

Since user primary group name is saved in variable $group (See install-init.in for
the gropu variable assignment) chown command should use $group instead $user as
group name.
Merge pull request #4901 from xwang2713/Ming_HPCC_9773

HPCC-9773 Change group variable from $user to $group in chown.

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>