Android Strict mode policy for notification

Question

I am using Strict mode in one of my main activity in onCreate method

   StrictMode.setVmPolicy(new StrictMode.VmPolicy.Builder()
                .detectAll()
                .penaltyLog()
                .penaltyDeath()
                .build());

The Activity has 4 fragments and when i click on the notification of GCM then a new instance of my activity is getting created rather than resuming my activity which is giving error and shutting down my activity.

Here is the error:

com.test E/StrictMode: class com.test.activity.TestActivity; instances=2; limit=1
                                                                  android.os.StrictMode$InstanceCountViolation: class com.test.activity.TestActivity; instances=2; limit=1
                                                                      at android.os.StrictMode.setClassInstanceLimit(StrictMode.java:1)
com.test W/System.err: StrictMode VmPolicy violation with POLICY_DEATH; shutting down.
com.test D/Process: killProcess, pid=15352
com.test D/Process: android.os.StrictMode.onVmPolicyViolation:1686 android.os.StrictMode.decrementExpectedActivityCount:2098 android.app.ActivityThread.performDestroyActivity:4052 

here is the configuration for intent filter for TestActivity.

<intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>

and Notification Builder

PendingIntent pendingIntent = PendingIntent.getActivity(this, REQ_CODE, intent,
                PendingIntent.FLAG_ONE_SHOT);
  notificationBuilder = new NotificationCompat.Builder(this);
        notificationBuilder.setSmallIcon(getNotificationIcon())
         .setContentTitle("GCM")
                .setContentText(message)
                .setAutoCancel(true)
                .setSound(defaultSoundUri)
                .setContentIntent(pendingIntent);
 NotificationManager notificationManager =
                (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);

        notificationManager.notify(NOTF_ID, notificationBuilder.build());

So where should i need to change the code so that the notification will open in single instance?