internal/nettest: skip unixpacket tests on netbsd/386

Updates golang/go#22927

Change-Id: I813b9ba92f9dd7e517385dc95df20691efee01a6
Reviewed-on: https://go-review.googlesource.com/80755
Reviewed-by: Benny Siegert <bsiegert@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

internal/nettest/stack.go

@@ -74,6 +74,11 @@ func TestableNetwork(network string) bool {
 		switch runtime.GOOS {
 		case "android", "darwin", "freebsd", "nacl", "plan9", "windows":
 			return false
+		case "netbsd":
+			// It passes on amd64 at least. 386 fails (Issue 22927). arm is unknown.
+			if runtime.GOARCH == "386" {
+				return false
+			}
 		}
 	}
 	return true