The name lookups are unrooted; the test should be unrooted too.
Correctly skips the tests if the DNS config specifies a domain
suffix that has a wildcard entry causing all unrooted names to resolve.

Change-Id: I80470326a5d332f3b8d64663f765fd304c5e0811
Reviewed-on: https://go-review.googlesource.com/36253
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>