As I understand it Google Omega and RAFT are two different things. Google Omega is Google's answer to Apache Mesos. Omega would need a service like Raft to understand what services are currently available. In short, Google Omega is not a service discovery service.
Actually, I think Google Omega is the next-generation scheduler after their original Borg scheduler, which in-turn inspired Mesos.
The design of Omega is quite different than Mesos. I really do recommend reading the Mesos & Omega papers, they are quite interesting.
And yes, Raft is a consensus algorithm for keeping a set of distributed state machines in a consistent state. Mesos actually uses ZooKeeper under the hood for master election, which uses its own consensus algorithm (ZAB - Zookeeper Atomic Broadcast).
