(Ryan to review)
Unability to cope with the situation that no node of particular cluster
can be contacted at certain luci pages gracefully.
Certain places (Failover Domains, Fence Devices, Resources, and Service
Groups tabs) within luci result in Error 500 message accompanied with
the tracebacks in the log when no cluster node can be concated
(and hence there is no knowledge about the cluster in question).
In the aforementioned cases, either "Unable to contact any of the nodes
in this cluster" or "No nodes from this cluster could be contacted.
The status of this cluster is unknown." is displayed as an appropriate
Unability to contact any cluster node will not cause disruptive