Those devices don't have 'device' propery, only 'l3_device', which
causes 'attempt to concatenate field 'device' (a nil value)' lua error.

Use 'l3_device' as a fallback in this case.

Signed-off-by: Jacek Konieczny <jajcus@jajcus.net>

Signed-off-by: Leong Hui Wong <wong.leonghui@gmail.com>

this allow us to stop using uci /var/state,
which is deprecated since forever

Signed-off-by: Etienne Champetier <champetier.etienne@gmail.com>

Signed-off-by: Stefan Weil <sw@weilnetz.de>

Signed-off-by: Etienne CHAMPETIER <etienne.champetier@free.fr>