app RIB ought to be special type of peer

Currently the app RIB is an iBGP peer. This means that app RIB routes aren't sent to ODL's iBGP peers.

using eBGP from ODL means we can't "fake" the next-hop (a major use-case for app RIB)

setting an iBGP peer to be an rr-client means ODL will fill in cluster-ID and originator-ID (which is undesirable) - plus I'm currently seeing an issue where due to incorrect cluster-ID/originator-ID we're not advertising app RIB routes to RR clients (though sure, that one should be fixed anyhow).

So what I'd prefer is for the app RIB to be a modified form of rr-client where cluster-id and originator-id are not filled in when advertising routes to iBGP peers (or RR clients).