Instead of converting the sysv script, you could trivially write your own, the following was tested against about 6 SNMP queries, the service stops and starts as expected. You may want to purge the sysv remnants.
# cat /etc/systemd/system/lsi_mrdsnmpd.service [Unit] Description=LSI SNMP Agent startup/shutdown script
Requires=network.target Requires=snmpd.service
After=network.target After=snmpd.service
[Service] Type=forking ExecStart=/etc/lsi_mrdsnmp/lsi_mrdsnmpagent -c /etc/snmp/snmpd.conf
[Install] WantedBy=multi-user.target
hth, jlc