net: some Windows DNS tests rely on CNAME flattening

[zhangyoufu]

Does this issue reproduce with the latest release?

Yes

What did you do?

go test -v net

What did you expect to see?

Test pass.

What did you see instead?

=== RUN   TestNSLookupMX
--- FAIL: TestNSLookupMX (0.04s)
    lookup_windows_test.go:37: no results

Comment

When I set Google DNS (8.8.8.8) as my DNS server, the test passed.
When I set OpenDNS (208.67.220.220) as my DNS server, the test failed.
Theses tests should not rely on whether CNAME flattening is available on a recursive DNS resolver.

[networkimprov]

@gopherbot add OS-Windows

cc @alexbrainman

[cagedmantis]

/cc @mikioh

[networkimprov]

cc @ianlancetaylor since mikioh is no longer active on the issue tracker.