net: allow longer timeout in dialClosedPort test on windows

The test expects the dial to take 1.0 seconds
on Windows and allows it to go to 1.095 seconds.
That's far too optimistic.
Recent failures are reporting roughly 1.2 seconds.
Let it have 1.5.

Change-Id: Id69811ccb65bf4b4c159301a2b4767deb6ee8d28
Reviewed-on: https://go-review.googlesource.com/12895Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/net/dial_test.go

@@ -249,7 +249,7 @@ func dialClosedPort() (actual, expected time.Duration) {
 	// On Windows, dialing a closed port takes roughly 1 second,
 	// but other platforms should be instantaneous.
 	if runtime.GOOS == "windows" {
-		expected = 1095 * time.Millisecond
+		expected = 1500 * time.Millisecond
 	} else {
 		expected = 95 * time.Millisecond
 	}