DNS lookup before ping

[vlasad]

#3333

[ghost]

I think the goal here is to add the failure in as a metric (field or tag) somehow, per the discussion in #3333

@danielnelson what do you reckon (given the various very valid points in that thread) is the best thing to do with this in the short term? I'm a little torn but to be honest, we dont mind - any of the options are way better than what we have today ;-)

[danielnelson]

I think we will want to send something in the metric instead of just returning an error. Also, we won't want to use the dns_query plugin or the testutil Accumulator. Let's continue discussing over on #3333