net: don't return errno from _C_res_nsearch

net: don't return errno from _C_res_nsearch

We ignore the value anyhow.

Change-Id: I1b1db7831c42bf852652236212812fd5cf258530
Reviewed-on: https://go-review.googlesource.com/c/go/+/457439
Reviewed-by: Damien Neil <dneil@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>