always_include_confirm_step preference seems broken

On a clean Spree 2.1.2 store I'm not able to have `always_include_confirm_step` preference working. 

Despite if I call `confirmation_required?` on the order it returns true, the confirmation step is not shown. 

I wrote a small failing test (on master branch) into spec/features/frontend/checkout_spec.rb which reproduces the issue:

```ruby
context "when Spree::Config[:always_include_confirm_step] is true" do
  before do
    Spree::Config[:always_include_confirm_step] = true
    # The following line doesn't help neither
    # Spree::Order.any_instance.stub :confirmation_required? => true
  end

  it "displays confirmation step", :js => true do
    add_mug_to_cart
    click_button "Checkout"

    fill_in "order_email", :with => "test@spreecommerce.com"
    fill_in_address

    click_button "Save and Continue" # delivery
    click_button "Save and Continue" # payment
    page.should have_content("Place Order") # fails here
  end
```