net: re check conf.goos even if it equals runtime.GOOS
This field is only for testing purposes, where we can't assume
that the conf value was initialized as expected for that GOOS.
This fixes the net tests on android.
Change-Id: I8432587f219a05adbb4d234a813467f876a764b2
Reviewed-on: https://go-review.googlesource.com/c/go/+/489975
Run-TryBot: Ian Lance Taylor <iant@golang.org> Reviewed-by: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com> Reviewed-by: Ian Lance Taylor <iant@google.com>