You can stop it from talking to activate, that will effectively stop IAP from talking to Central.
How to stop IAP from talking to activate? either of below options will work:
1. Make IAP's time from 1970s. SSL to activate will fail as a result.
2. stop communication to device.arubanetworks.com using ACLs on wired network.
3. stop DNS server assigned to IAP via DHCP, from replying resoultion to device.arubanetworks.com