Symptom:
Under random load balancing designs, no AP HA settings, and AP load balancing between multiple MG WLCs, the CAPWAP APs do not properly random load balance via capwap discovery to learned MG WLCs

Conditions:
AP will have its capwap private-config fully cleared from WLC or directly on AP, and then AP is reloaded.
AP will obtain a WLC IP address via option 43.
The AP will successfully register to the option 43 WLC, and now learn the other MG WLCs.
The AP should now send unicast discoveries to these MG WLCs and decide to move to the least loaded WLC if possible.
Instead, the AP only sends a broadcast discovery out. 
The AP will not move off to other least loaded WLCs as random load balancing requires.