[VLAN]: Add a net argument to proc init and cleanup calls.

All proc files will be created in each net, so prepare them for
this change now, not to mess it with real creation patch.

The net != &init_net checks in them are for git-bisect sanity,
but I will drop them soon.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Acked-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>