net: skip TestDialTimeout subtests on Windows if Dial returns WSAECONNREFUSED

net: skip TestDialTimeout subtests on Windows if Dial returns WSAECONNREFUSED

Since we have only seen this failure mode on windows/arm64,
we do not skip on the Go project's windows/amd64 builders
so that we will be more likely to find out whether this failure mode
is specific to arm64.

Also simplify the ECONNRESET check, since I've remembered that the
error_*_test.go files exist.

Fixes #62359.
Updates #56876.

Change-Id: I17bd678486f3d3ec3363a45986a711f570b013d0
Reviewed-on: https://go-review.googlesource.com/c/go/+/524455
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Bryan Mills <bcmills@google.com>
Reviewed-by: Damien Neil <dneil@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Run-TryBot: Bryan Mills <bcmills@google.com>