Fix for /var/run/clamav on CentOS 7

Fix for https://bugs.vestacp.com/issues/393

Solution taken from https://forum.vestacp.com/viewtopic.php?f=40&t=11044#p42704

install/rhel/7/clamav/clamd.service

@@ -4,6 +4,8 @@ After = syslog.target nss-lookup.target network.target
 
 [Service]
 Type = simple
+ExecStartPre = /usr/bin/mkdir -p /var/run/clamav
+ExecStartPre = /usr/bin/chown -R clam:clam /var/run/clamav
 ExecStart = /usr/sbin/clamd -c /etc/clamd.conf
 Restart = on-failure
 PrivateTmp = true