It turns that, at least in cyrus 3, the cyr_systemd_helper script will
end up wiping out your databases every time the daemon starts. It was
something that was needed to handle the horror that was Berkeley
DB/Sleepycat DB/whatever it's called today, but Cyrus no longer supports
BDB and so there's no point.
An extra systemd service file will call sscg to setup a secure initial
certificate if it does not exist. The new default imapd.conf file will
reference that cert.