raft.go
func (r *Raft) quorumSize() int {
	voters := 0
	for _, server := range r.configurations.latest.Servers {
		if server.Suffrage == Voter {
			voters++
		}
	}
	return voters/2 + 1
}
func (r *Raft) quorumSize() int {
	voters := 0
	for _, server := range r.configurations.latest.Servers {
		if server.Suffrage == Voter {
			voters++
		}
	}
	return voters/2 + 1
}
// quorumSize is used to return the quorum size. This must only be called on
// the main thread.
// TODO: revisit usage