With this we make it easier to write correct network families as less
details need to be taken into account, as well in the current state we
make the non-refcounting protocols (the ones still keeping deliver_to_old_ones
in the tree) suck less. 8)

Left a WARN_ON in sk_del_node_init for a while, so that we can catch cases
where we're using __sock_put on a struct sock that has refcnt == 1, which
is not the case for all the ones I tested.