workloads/aitutu: Improve reliability of results extraction

Wait for the device to become idle before attempting to extract
the test scores.

wa/workloads/aitutu/uiauto/app/src/main/java/com/arm/wa/uiauto/aitutu/UiAutomation.java

@@ -101,6 +101,7 @@ public class UiAutomation extends BaseUiAutomation {
     }
 
     public void getScores() throws Exception {
+        mDevice.waitForIdle(5000);
         UiSelector selector = new UiSelector();
         //Declare the models used
         UiObject imageMod =