Fixing testOverview test

Apparently, we can't generally expect that flinging to and
fro will return Overview to the original task, especially
if the device performance is low.

Now starting the expected task explicitly.

Test: presubmit
Bug: 182794819
Change-Id: Ia2931f4f3005c46dd72990c247a90f9010b9b8d5
diff --git a/quickstep/tests/src/com/android/quickstep/TaplTestsQuickstep.java b/quickstep/tests/src/com/android/quickstep/TaplTestsQuickstep.java
index 0fe5432..5ffe315 100644
--- a/quickstep/tests/src/com/android/quickstep/TaplTestsQuickstep.java
+++ b/quickstep/tests/src/com/android/quickstep/TaplTestsQuickstep.java
@@ -120,6 +120,7 @@
                 getCurrentOverviewPage(launcher) < currentTaskAfterFlingForward));
 
         // Test opening a task.
+        startTestActivity(2);
         OverviewTask task = mLauncher.pressHome().switchToOverview().getCurrentTask();
         assertNotNull("overview.getCurrentTask() returned null (1)", task);
         assertNotNull("OverviewTask.open returned null", task.open());