Revert "Remove global updateInbox method"

This reverts commit 1c70293bba.

This broke tests by blocking the database deletion during test
setup.

js/background.js

@@ -18,6 +18,8 @@
 
     textsecure.protocol_wrapper.startWorker();
 
+    ConversationController.updateInbox();
+
     extension.onLaunched(function() {
         storage.onready(function() {
             if (textsecure.registration.isDone()) {