Fix "invisible user switch applet" problem
    
    There is a period of time when first starting up that
    get_user calls will fail to function properly because
    it communicates with the accounts service synchronously
    while the user manager is doing it's initial bring up
    asynchronously.
    
    This package makes get_user asynchronous like the rest of
    the user manager code, and also enforces an ordering
    requirement that get_user requests are deferred until
    after the user manager is loaded.
    
    The upshot is that the user switcher should consistently
    present the user's name now when the accounts service
    is disabled.