Report something sensible for out-of-quorum clusters
Currently, if there is quorum but one or more mons is out of it, we report that sanely. However, when a cluster loses quorum it stops responding to our requests for status, and we fall back to reporting that we lost contact with the cluster (which is only true in the technically-correct sense).
Calamari 1.0 partway dealt with this by attempting to open a TCP connection to any mon which appeared to be out of quorum, do indicate that it was 'up' but not 'in'. However, it would still fall over if there was no quorum to talk to at all.
We should be able to do a better job for 2.0 with ServerMonitor's knowledge of a mon service being running or not running at some point in the recent past.