failure_app::recall doesn't take into account relative_url_root

[stanhu]

When a login failure occurs, Warden sends back a full path in attempted_path, but devise's failure_app assumes the path does not contain a relative URL root and assigns it to PATH_INFO:

  def recall
      env["PATH_INFO"]  = attempted_path
      flash.now[:alert] = i18n_message(:invalid) if is_flashing_format?
      self.response = recall_app(warden_options[:recall]).call(env)
    end

For example, suppose:

1. relative_url_root = /base_app
2. attempted_path = /base_app/resource.
3. In this case, PATH_INFO is assigned /base_app/resource.
4. However, SessionController::store_redirect_path will call request.fullpath, which then makes the path /base_app/base_app/resource. Note the redundant base_app.

PATH_INFO should only contain the part of the path that excludes the relative URL root, since SCRIPT_NAME includes the relative URL part (see http://api.rubyonrails.org/classes/ActionDispatch/Routing/UrlFor.html) for more details.