Don't show 'Initializing' for custom start views

This makes me think the throbber shouldn't be rendered here at all, it should be rendered in each view by a shared base class. Maybe something like [BaseView](https://github.com/mozilla/spartacus/blob/master/public/js/views/base.js) called ``TaskView`` (or whatever) to indicate that the view requires some initialization task and should show a loading throbber. All necessary views could inherit from that to get the throbber.