net/http: disable recently-introduced flaky test on Windows

Disable it until it's debugged so it doesn't hide other real
problems on Windows. The test was known to be unreliable
anyway (which is why it only needed 1 of 20 runs to pass), but
apparently it never passes on Windows. Figure out why later.

Update #7634

LGTM=alex.brainman
R=adg, alex.brainman
CC=golang-codereviews
https://golang.org/cl/80110043

src/pkg/net/http/transport_test.go

@@ -1840,6 +1840,9 @@ func TestTransportTLSHandshakeTimeout(t *testing.T) {
 // Trying to repro golang.org/issue/3514
 func TestTLSServerClosesConnection(t *testing.T) {
 	defer afterTest(t)
+	if runtime.GOOS == "windows" {
+		t.Skip("skipping flaky test on Windows; golang.org/issue/7634")
+	}
 	closedc := make(chan bool, 1)
 	ts := httptest.NewTLSServer(HandlerFunc(func(w ResponseWriter, r *Request) {
 		if strings.Contains(r.URL.Path, "/keep-alive-then-die") {