chore(registry): drop irrelevant comment
refactor(registry): update etcd paths
refactor(scheduling): Major refactor to move to the new scheduling model

* Users can control what services should be running on a given machine
  through the /coreos.com/coreinit/machines/<machine bootid>/schedule/
  endpoint. Simply create a new key (i.e. nginx.service) where the value
  is a valid systemd Unit file. Delete this key if the service should
  be stopped.
* coreinit reports the current states of the necessary services at the
  /coreos.com/coreinit/machines/<machine bootid>/units/ endpoint. The
  keys should reflect what is in the schedule/ directory, while the
  values will be the current state of the service reported by systemd.