Split the network testing component of the validate-host rule into a
separate task, so it can be retried a couple of times in case
something is a bit slow about bringing up external networking. Add
failure collection of unbound logs if they appear to be in some common
locations (such as will be there on infra nodes).
Change-Id: Id12f1ba064fa2e5f75b9a5cfba76d238d23d3f57