Are you running 4.1?
If so, you can use the new zones feature which would be similar to a controller AP group.
From the 4.1 User Guide (page 84):
All APs in a cluster use the same SSID configuration including master and slave IAPs. However, if you want to assign an SSID to a specific IAP, you can configure zone settings for an IAP.
The following constraints apply to the AP zone configuration:
- An IAP can belong to only one zone and only one zone can be configured on an SSID.
- If an SSID belongs to a zone, all IAPs in this zone can broadcast this SSID. If no IAP belongs to the zone configured on the SSID, the SSID is not broadcast.
- If an SSID does not belong to any zone, all IAPs can broadcast this SSID. You can add an AP zone by through the UI or CLI.