title: robust_connection from aio_pika not reconnecting
body: <p>I have the following application with asyncio and iohttp. On start of the application I start the web interface (iohttp) and the aio_pika consumer. Everything works so far for me the only thing is that the robut connection does not try to reconnect. When I restart my rabbit docker image I get this log message: </p>
  
  <pre><code>[2019-11-21 14:05:13,069] INFO: Connection to amqp://guest:******@127.0.0.1/ closed. Reconnecting after 5 seconds. 
  </code></pre>
  
  <p>But than I receive the following exception and it doesnt reconnect:</p>
  
  <pre><code>  File "/usr/lib64/python3.7/asyncio/selector_events.py", line 804, in _read_ready__data_received
      data = self._sock.recv(self.max_size)
  ConnectionResetError: [Errno 104] Connection reset by peer
  
  Traceback (most recent call last):
    File "/home/ghovat/.local/share/virtualenvs/zendesk-wrapper-BdIlfSJk/lib/python3.7/site-packages/aio_pika/robust_connection.py", line 148, in reconnect
      await self.connect()
    File "/home/ghovat/.local/share/virtualenvs/zendesk-wrapper-BdIlfSJk/lib/python3.7/site-packages/aio_pika/robust_connection.py", line 134, in connect
      await self.__cleanup_connection(e)
    File "/home/ghovat/.local/share/virtualenvs/zendesk-wrapper-BdIlfSJk/lib/python3.7/site-packages/aio_pika/robust_connection.py", line 96, in __cleanup_connection
      self.connection.close(exc),
  AttributeError: 'NoneType' object has no attribute 'close'
  </code></pre>
  
  <p>Should the robust connection not try to reconnect again? The problem with <code>connection reset by peer</code> seems to be the rabbit startup which needs couple of seconds.</p>
  
  <p>This is how I start the application:</p>
  
  <pre><code>def loop_in_thread(loop):
      asyncio.set_event_loop(loop)
      connection = loop.run_until_complete(main(loop))
      try:
          loop.run_forever()
      finally:
          loop.run_until_complete(connection.close())
  
  
  if __name__ == "__main__":
      app = setup_app()
      loop = asyncio.new_event_loop()
      t = threading.Thread(target=loop_in_thread, args=(loop,))
      t.start()
      web.run_app(app)
  </code></pre>
  
  <p>This is how my consumer looks like:</p>
  
  <pre><code>async def main(loop):
      connection = await aio_pika.connect_robust(
          "amqp://guest:guest@127.0.0.1/", loop=loop
      )
  
      queue_name = "test_queue"
  
      print("jdklasjkl")
  
      async with connection:
          # Creating channel
          channel = await connection.channel()
  
          # Declaring queue
          queue = await channel.declare_queue(
              queue_name, auto_delete=False
          )
  
          async with queue.iterator() as queue_iter:
              async for message in queue_iter:
                  async with message.process():
                      print(message.body)
  
                      if queue.name in message.body.decode():
                          break
  </code></pre>