fix bulk updates overlapping with shared state
new cc request protocol

* shorter subject (health.(stop|start))
* includes version in stop requests
* includes running counts by version in both requests
fix getting running count of instances
fix wrong local variable usage
send instance versions in stop requests
make logging less verbose and more structured
fix case where HM would kill too many instances

this would happen if an instance designated for death appeared before
the rest of the instances; it would count that doomed instance in the
running count, and cause later instances to be designated "extra"