hostapd: Fix premature beacon set during association handling

hostapd: Fix premature beacon set during association handling

Currently, during association handling, if any of the iface parameters
changes due to some reason, it calls ieee802_11_set_beacons() function.
This function sets beacon for the all the BSSes in that iface even if
the beacon was not set already. This leads to setting the beacon
prematurely for some BSSes which was intentionally not started.

Fix the above issue by calling ieee802_11_update_beacons() function
instead. This function only updates the beacon if it was already set.

While at it, do the same while freeing STA entry.

Signed-off-by: Aditya Kumar Singh <quic_adisi@quicinc.com>