Add a command to upgrade and/or reconfigure Docker

We have a 'bootstrap-servers' command to bootstrap servers, but lack commands to perform more specific day 2 operations. A common requirement is to be able to upgrade, reconfigure, or simply restart docker. Once the control plane has been deployed, we need to be careful about this, to avoid taking everything down simultaneously which can lead to loss of quorum and overload when services return. We should:

* Properly roll through hosts using --serial?
* Can we guarantee not to lose quorum?+1
* Consider live-restore to make docker restarts less dangerous