net: ignore edns0 option in resolv.conf
net: ignore edns0 option in resolv.conf

We use EDNS(0) by default. No need to fall back to netdns=cgo if we
see a explicit request for EDNS(0) in resolv.conf.

For #51153

Change-Id: I135363112e3de43ce877aad45aba71d1448068b7
Reviewed-on: https://go-review.googlesource.com/c/go/+/415579
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@google.com>
Auto-Submit: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@google.com>
TryBot-Result: Gopher Robot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Run-TryBot: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@google.com>
Run-TryBot: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>
Reviewed-by: Damien Neil <7e091e9a80da888fcd7836fd3c6b7b85f4677c12@google.com>

golang/go,golang/go,golang/go,golang/go,golang/go,golang/go,golang/go,golang/go