Perform any filter operations that are required for routes that we originate.
Currently this only involves prepending our AS number on IBGP peers. We assume that on EBGP peers the AS number has already been prepended.
| OriginateRouteFilter (const AsNum &as_num, PeerType peer_type)
|bool filter (InternalMessage<A>& rtmsg)
Reimplemented from BGPRouteFilter.