ftpd: stop using -g flag for /bin/ls

In 3bfbb521 the behaviour of ls was changed such that -g was no longer
a noop for compatibility with BSD 4.3, but instead changed the output
of long mode to exclude the owner of the file and display only the
group.

Update how FTPd invokes ls to restore the previous behaviour

Reported-by: Andrew Fengler <andrew.fengler@scaleengine.com>
Reviewed-by: jrtc27, des, imp
MFC after: 3 days
Sponsored-by: ScaleEngine Inc.
Fixes: 3bfbb521fef5 ("ls: Improve POSIX compatibility for -g and -n.")