Ensure that Launcher Activity has an exclusive task

-> enforce this at the activity level by giving it an empty affinity
-> the system should probably enforce this, so this is a work around for now

issue 21880868

Change-Id: Iaba4d87781c7fc82ee6c2838c013e01081cdbf9d

AndroidManifest.xml

@@ -83,6 +83,7 @@
             android:windowSoftInputMode="adjustPan"
             android:screenOrientation="nosensor"
             android:resumeWhilePausing="true"
+            android:taskAffinity=""
             android:enabled="true">
             <intent-filter>
                 <action android:name="android.intent.action.MAIN" />