Avoids multiple coordinators trying to write updated cluster-wide fault
events. Instead, they are now only written by the primary (or the
incoming primary if still in a transition).
Instead of using random hex characters from an md5sum, use a nice name
in all-caps similar to how Ceph does. This further helps prevent dupes
but also permits a changing health delta within a single event (which
would really only ever apply to plugin faults).
Since we already had a "details" field, simply move where it gets added
to the message later, in generate_fault, after the main message value
was used to generate the ID.
Adjusts ordering and ensures that node health states are included in
faults if they are less than 50%.
Also adjusts fault ID generation and runs fault checks only coordinator
nodes to avoid too many runs.
Joshua Boniface