It was possible to hit a race condition between WPS_CANCEL and
immediately following WPS_PIN command. Wait for a disconnection event to
avoid that. This was seen with the following test case sequence:
ap_wpa2_psk_supp_proto_wrong_group_key_len ap_wps_probe_req_ie_oom
Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>