Fix updating of lock icon and tool tip in editor tool bar

Since the IEditor changed signal removal it was not updating them at
all, and before that it was only updating them in one of the editor
views in case of splits.

Change-Id: I8c604b64d03f6ea243e67fab52692b5b17795c32
Reviewed-by: Eike Ziller <eike.ziller@digia.com>