The FQDN should be caputed through the Agentless Managment Service "AMS" running on the ESXi server. This is installed by default if you are using HP image but can also be added to a vmaware image. This can be downloaded from HP.
To check the service
To start or stop Agentless Management Service, use the command appropriate for your environment:
• VMware ESX 4.1U2 Classic:
– /etc/init.d/hp-ams [start | stop | restart | status]
• VMware ESXi 4.1U2:
– /usr/sbin/hp-ams.sh [start | stop | restart | status]
• VMware ESXi 5.x:
– /etc/init.d/hp-ams.sh [start | stop | restart | status]
I've attached a guide that speak to agentless monitoring