Set Alert timeout to FOREVER to avoid timing issues while running tests; update AlertTest reference image without the scrollbar

tests/automation.js

@@ -19,7 +19,7 @@ casper.options.onWaitTimeout = function() {
 };
 
 var gfxTests = [
-  { name: "gfx/AlertTest", maxDifferent: 3279 },
+  { name: "gfx/AlertTest", maxDifferent: 0 },
   { name: "gfx/CanvasTest", maxDifferent: 0 },
   { name: "gfx/DrawRegionTest", maxDifferent: 0 },
   { name: "gfx/ImageRenderingTest", maxDifferent: 266 },

tests/gfx/AlertTest.java

@@ -13,6 +13,7 @@ public class AlertTest extends MIDlet {
 
     public void startApp() {
         alert = new Alert("Hello World", "Some text", null, AlertType.INFO);
+        alert.setTimeout(Alert.FOREVER);
         display.setCurrent(alert);
 
         try {