main: hook up with discovery

@philips We need to modify current discovery to create _config/size key when new the token.
tested on my local machine, works. 
- etcd: error: the cluster using discovery https://discovery.etcd.io/123 has already started with all 5 members
- etcd: error: the cluster doesn’t have a size configuration value in https://discovery.etcd.io/123/_config
- etcd: warn: ignoring discovery URL as an initialized and has a valid log in /var/lib/etcd