Android: Remove allowBackup from manifest

Setting AllowBackup false to avoid storing user critical information on
google cloud. It also solves problems that occur at startup after 
uninstalling / reinstalling the app. Sometimes we have partial data from
google cloud that create weird behaviour.  

Change-Id: If3e2f90359a215a9cb4fd03678ca44a851ca1d0e
diff --git a/ring-android/app/src/main/AndroidManifest.xml b/ring-android/app/src/main/AndroidManifest.xml
index 16ae326..d151ad7 100644
--- a/ring-android/app/src/main/AndroidManifest.xml
+++ b/ring-android/app/src/main/AndroidManifest.xml
@@ -69,7 +69,7 @@
 
     <application
         android:name=".application.RingApplication"
-        android:allowBackup="true"
+        android:allowBackup="false"
         android:icon="@drawable/ic_launcher"
         android:label="@string/app_name"
         android:resizeableActivity="true"