avoid refreshing ember flicker ui.

foo.coffee

App.WorkersIndexController = Ember.ArrayController.extend
    refresh: ->
        console.log 'refreshing workers'
        @set 'refreshing', App.Worker.find()

    update: (->
        refreshing = @get 'refreshing'
        return unless refreshing.get('isLoaded')
        Ember.run =>
            @set 'content', refreshing
    ).observes('refreshing.isLoaded')