Updates to x/net git rev a8b92947779 for CL 80755

Updates #22927

Change-Id: I84aad75afd954c9a6c57ad9a76328b99f1dc74a1
Reviewed-on: https://go-review.googlesource.com/80758
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Benny Siegert <bsiegert@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>