ref(*): never use etcdctl with --no-sync

@aledbf brought up a good point - when using etcdctl, we connect
to only one etcd daemon in the cluster and use the `--no-sync`
flag so the daemon doesn't have to sync with the other cluster
members. However, this can be dangerous when we're dealing with larger
clusters that have etcd daemons in standby mode (i.e. not peers).

See https://github.com/coreos/etcd/blob/master/Documentation/api.md#cluster-config
and https://github.com/coreos/etcd/blob/master/Documentation/design/standbys.md
for details on standby nodes.

This isn't an issue for most clusters as the activeSize by default appears
to be 9:
```console
ore@deis-1 ~ $ curl -L http://127.0.0.1:7001/v2/admin/config
{"activeSize":9,"removeDelay":1800,"syncInterval":5}
```

However, we definitely don't want to run into issues on larger clusters.