I don't have Extreme Access Points and I had a similar issue with my Aerohive Access Points. I found that they would go offline but still show power draw on the Extreme switch ( zombie mode I called it ).
In the Aerohive management system, I had LLDP data for the Access Point giving me the switch MAC and port for the switch the Access Point was connected to.
I wrote a script that did the following:
 
- Connect via REST API to may wireless management system to get a list of potential "zombie" access points. 
 
 
 - Connect to Extreme Management Center via XML API to get a list of all switches 
 
 
 - Resolve the switch MAC in the the Access Point data to a switch IP address by building a MAC keyed table of my switches 
 
 
 - Connect to the switch and interrogate the port state ( basically is current being drawn ) 
 
 
 - Toggle PoE on the switch port 
 
 
 - Wait for five minutes to see if I can detect that the AP is now up ( its MAC visible on the port with "show fdb port xx" command )
 
I could share the code if anybody wanted to use it as the basis for a similar script. The Extreme elements would be reusable and the Aerohive stuff would show a template for implementing on another Wireless system.