netnsid: update device only if netnsid matches.

netnsid: update device only if netnsid matches.

Recent kernels provide the network namespace ID of a port,
so use that to discover where the port currently is.

A network device in another network namespace could have the
same name, so once the socket starts listening to other network
namespaces, it is necessary to confirm the netnsid.

Signed-off-by: Flavio Leitner <fbl@redhat.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>