Clustering (and maybe config) should be coordinated with etcd

[scottferg]

@foresmac large change here, but one that would be valuable to use on other projects as well. etcd (https://github.com/coreos/etcd) has a very nice Go client that would work well in Vip. Currently all Vip instances are running as naive instances that are unaware of other groupcache peers. Theoretically a Vip instance should be able to come online, ping etcd for other Vip instances, and establish connections to build out the p2p network. This is necessary for Vip clusters to grow organically. The old method of querying for EC2 tags was very hamfisted and worked off and on.

Additionally, any Vip configuration could also live in Etcd (since that's what it's for). That would simplify deployments immensely.

[scottferg]

Etcd doesn't work in a practical way for what we'd need. Closing this in favor of running vip instances behind github.com/vokal/freeway