model: introduce the state VA and its constants
odemisd: start upgrading mdupdater to become dynamic

still need the main part: subscribe to .alive
odemisd: update md updates when the components change

listen to .alive
odemisd: don't try to stop the containers twice on normal ending

once the container is closed, a call to terminate fails badly, which is not nice
at least in the log, and it's not useful to try to kill everything twice anyway.
driver pigcs: raise HwError in case of recoverable hardware error

allows the backend to automatically try reconnecting.