dpif-netlink: Support rtnetlink port creation.

dpif-netlink: Support rtnetlink port creation.

In order to be able to add those tunnels, we need to add code to create
the tunnels and add them as NETDEV vports. And when there is no support
to create them, we need to fallback to compatibility code and add them
as tunnel vports.

When removing those tunnels, we need to remove the interfaces as well,
and detecting the right type might be important, at least to distinguish
the tunnel vports that we should remove and the interfaces that we
shouldn't.

Co-authored-by: Thadeu Lima de Souza Cascardo <cascardo@redhat.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@redhat.com>
Signed-off-by: Eric Garver <e@erig.me>
Signed-off-by: Joe Stringer <joe@ovn.org>