PUSH-287 Make sure that the callback registered with LocalStorageNotificationBroadcaster is invoked only when the localStorage slot (created by  LocalStorageNotificationBroadcaster instance) is modified.

git-svn-id: http://anonsvn.icesoft.org/repo/icepush/trunk/icepush@38758 1de00972-ac04-4911-a46b-06793c8d78d9