swallow agent_listener calls

agent_listener.rb

class AgentListener
  def initialize(app, options = {})
    @app = app
  end

  def call(env)
    if /^\/agent_listener/ =~ ::Rack::Request.new(env).path_info
      [404, {}, ['']]
    else
      @app.call(env)
    end
  end
end