DNS responses which do not contain answers of the requested type return
errNoSuchHost, the same error as rcode name error. Prior to
golang.org/cl/37879, both cases resulted in no additional name servers
being consulted for the question. That CL changed the behavior for both
cases. Issue #25336 was filed about the rcode name error case and
golang.org/cl/113815 fixed it. This CL fixes the no answers of requested
type case as well.

Fixes #27525

Change-Id: I52fadedcd195f16adf62646b76bea2ab3b15d117
Reviewed-on: https://go-review.googlesource.com/133675
Run-TryBot: Ian Gudger <igudger@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>