title: form_for does not append the action
body: <p>I have this <strong>html.erb</strong> rails code : </p>
  
  <pre><code>&lt;%= form_for(:dash_action, method: :post, url: {controller: 'brokers', action: 'dashboard'}) do |f| %&gt;
    &lt;%= f.submit("Suchen", class: "btn btn-primary", id: "change_status") %&gt;    
  &lt;% end %&gt;
  </code></pre>
  
  <p>When I check the generated HTML code, I see this for the <em>form element</em> : </p>
  
  <pre><code>&lt;form action="/brokers" accept-charset="UTF-8" method="post"&gt;
  </code></pre>
  
  <p>But I expect to see this as action: <strong>action="/brokers/dashboard"</strong></p>
  
  <p>Whats going wrong ? </p>
  
  <p>......................................................</p>
  
  <p>Here all brokers relates routes: </p>
  
  <pre><code>  get 'brokers/login_page'
    get 'brokers', to: 'brokers#dashboard'
    post 'brokers/dashboard', to: 'brokers#dashboard'
    post 'brokers/eval_login', to: 'brokers#eval_login'
    get 'brokers/logout'
    get 'brokers/edit_order_now'
  </code></pre>
  
  <p>Also when I do a  <code>url_for(controller: 'brokers', action: 'dashboard')</code> 
  I got only : 
  /brokers</p>