net/http: mark TestTLSServerClosesConnection as flaky on all systems

Fixes #14195

Change-Id: I245b3ca3fd7d1a76aa95f2e058f8432ba5ce31ee
Reviewed-on: https://go-review.googlesource.com/19160
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Russ Cox <rsc@golang.org>

src/net/http/transport_test.go

@@ -2208,9 +2208,8 @@ 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")
-	}
+	setFlaky(t, 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") {