Fix bug in the new notification sample.

Change-Id: I021c5f374857d1affdddd8be37c0f441aaf14c95
diff --git a/samples/ApiDemos/AndroidManifest.xml b/samples/ApiDemos/AndroidManifest.xml
index 9cd9d95..bcb0fcb 100644
--- a/samples/ApiDemos/AndroidManifest.xml
+++ b/samples/ApiDemos/AndroidManifest.xml
@@ -631,7 +631,8 @@
         <activity android:name=".app.IncomingMessageInterstitial"
                 android:label="You have messages"
                 android:theme="@style/ThemeHoloDialog"
-                android:launchMode="singleInstance"
+                android:launchMode="singleTask"
+                android:taskAffinity=""
                 android:excludeFromRecents="true">
         </activity>
 <!-- END_INCLUDE(interstitial_affinity) -->