[sudo-users] disable logging successful commands to systemd journal

[Todd C. Miller]

FYI, sudo 1.8.19 will allow you to disable successful or failed
sudo attempts using a priority of "none".  E.g.

Defaults syslog_goodpri=none

This is not present in the current sudo 1.8.19 beta but will be in
sudo 1.8.19b2.

 - todd