Just to add some context, be aware that many Xinetd configurations now have cumulative log settings by default- meaning that service-based log settings are appended to the default settings in /etc/xinetd.conf. You will see this if the configs use += instead of = to assign their log_on_success and log_on_failure settings.
The quick fix is to either use = in your service-based configs under /etc/xinetd.d/ to override the defaults, or else you can blank out the default settings for log_on_success or log_on_failure in /etc/xinetd.conf and let the service-based configs "append" their own settings as-needed.