https://src.fedoraproject.org/rpms/clamav/c/cf32b14aa9a58dcbf3a1e77a1d5871fc67f26b78?branch=epel7 still breaks existing installations, revert to the old behaviour with a cronjob, please. https://bugzilla.redhat.com/show_bug.cgi?id=1800226 has been filed.

As of clamav-update-0.101.5-7.el7, there is no more cronjob (while it existed at clamav-update-0.101.5-1.el7). It is IMHO not acceptable for existing RHEL/CentOS systems to change a package that drastically, that systemctl enable clamav-freshclam.service gets suddenly mandatory while it was previously not. System administrators of RHEL/CentOS systems expect that running yum update without further interventions keeps the system running and the configuration unchanged.

Introducing clamav-freshclam.service without an automagic upgrade path breaks existing unattended installations. Please introduce a proper %post scriptlet for this. And why is it called clamav-freshclam.service rather freshclam.service?

From /etc/clamav-unofficial-sigs/os.conf:

$ /sbin/service clamd try-restart
Usage: clamd {start|stop|status|restart|reload|condrestart}
$ 

Please change in /etc/clamav-unofficial-sigs/os.conf

clamd_restart_opt="/sbin/service clamd try-restart"

to

clamd_restart_opt="/sbin/service clamd condrestart"

That's restart only if the service is running and should be equivalent to the systemd variant.