F21 systemd log flood - how to stop

[Andy Hairston]

I have a near-stock installation of Fedora 21, and am experiencing the 
systemd log flood mentioned previously 
(https://lists.fedoraproject.org/pipermail/fedora-server-list/2014-May/001126.html). 
How do I get systemd to stop putting massive amounts of information into 
/var/log/messages for routine cron jobs? I tried setting LogLevel=warn 
in /etc/systemd/system.conf and rebooting, but this had no effect.