Thanks to Zenoss Community member Jose Gerez for updating the Fortigate SNMP Monitor ZenPack.  This ZenPack provides a /Network/Router/Firewall/Fortigate Device Class and a Fortigate template that can be bound to monitor CPU usage, Memory Utilization and Number of Sessions for a Fortigate Firewall.  Jose converted it to a Zenoss 2.2 and later .egg.

Thanks Jose!