flags/urls: reject url without port

For now, if etcd receives a url without port, it will listen on a random
port, which is useless.
etcdserver: publish self info when start
etcdserver: minimize input info
etcdserver: move grep member logic into publish func
Merge pull request #1219 from unihorn/148

flags/urls: reject url without port
Merge pull request #1201 from unihorn/143

etcdserver: publish self info when start
etcdserver: apply config change on cluster store