or handling

In my understanding we never call .disconnect() when .probe()
returns error. Change .probe() to return error all cases it cannot
handle given interface and simplify .disconnect() handling.

Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
§d½Æ•