I don't know that you can disable this function any longer... The Cloud discovery agent is built into Ruckus AP firmware with the purpose of checking our AP Registrar which notifies APs of their designated controller IP/FQDN, so an AP will go to the Cloud and not check locally for a controller in the case of our Cloud Wi-Fi platform, and large providers use APIs to configure their AP/Controller provisioning details this way too.
If you want to use a Solo AP along side ZD managed APs, use this command via SSH into the AP(s):
set director ip 188.8.131.52 184.108.40.206 reboot
This command will persist after a reboot, but not a factory default. I hope this is helpful.