Simplifying switching to home for some tests

Change-Id: I696d0267a2c36a18080396657bed07f7b1654a7d

tests/src/com/android/launcher3/ui/widget/AddWidgetTest.java

@@ -55,7 +55,7 @@ public class AddWidgetTest extends AbstractLauncherUiTest {
 
     private void performTest() throws Throwable {
         clearHomescreen();
-        mActivityMonitor.startLauncher();
+        mDevice.pressHome();
 
         final LauncherAppWidgetProviderInfo widgetInfo =
                 TestViewHelpers.findWidgetProvider(this, false /* hasConfigureScreen */);