Scenario:
- have ethernet connection as unmanaged.
- create (or have) a suitable profile for the connection.
- make the device as managed. No default wired connection gets
created.
- delete the profile.
Note that NMManager does in manager_device_state_changed():
»···if (NM_IN_SET (new_state,
»··· NM_DEVICE_STATE_UNAVAILABLE,
»··· NM_DEVICE_STATE_DISCONNECTED))
»···»···nm_settings_device_added (priv->settings, device);
that means, when the device the next time goes through
UNAVAILABLE/DISCONNECTED states, we will suddenly create the
default "Wired connection 1" profile.
That doesn't seem right. When a device is suitable to have a
default-wired connection, we should only check once whether to
create it. We should not retry that later. The !no-auto-default
mechanism exists so we can start NetworkManager without a profile for
the device. It doesn't mean that we later one (after previously deciding
not to create a profile), we still create it.
