wpa_supplicant currently logs CTRL-EVENT-AUTH-FAILED errors when
authentication fails, but doesn't expose any property to the D-Bus
interface related to this.
This change adds the "AuthStatusCode" property to the interface, which
contains the IEEE 802.11 status code of the last authentication.
Signed-off-by: Alex Khouderchah <akhouderchah@chromium.org>