sqs.changeMessageVisibility according to [this](https://docs.aws.amazon.com/AWSSimpleQueueService/latest/APIReference/API_ChangeMessageVisibility.html#API_ChangeMessageVisibility_Examples) makes a request directly to the Queue's URL rather than via the SQS Endpoint. (I'm already setting SQS endpoint to LOCALSTACK_HOSTNAME - makes no difference for this call)..

In localstack the queue URL host returned is by default set to the value of HOSTNAME_EXTERNAL, which I'm setting to localstack, but calling this method within a lambda, does not work and I get the error:

```
UnknownEndpoint: Inaccessible host: `localstack'. This service may not be available in the `us-east-1' region. 
```

So, how can I make the queue URL accessible from within a lambda using localstack? Effectively I need to make **http://localstack** accessible from within lambda.

I'm using the following cmd to start localstack:

```
LAMBDA_EXECUTOR=docker-reuse DEBUG=1 LAMBDA_REMOTE_DOCKER=0 DATA_DIR=/tmp/localstack/data HOSTNAME_EXTERNAL=localstack localstack start
```
aws_stack.create_sqs_queue(self.TEST_SQS_QUEUE)
        
        result = connect_api_gateway_to_sqs('test_gateway4', stage_name=self.TEST_STAGE_NAME,
            queue_arn=self.TEST_SQS_QUEUE, path=self.API_PATH_DATA_INBOUND)
        
        test_data = {'spam': 'eggs'}
        url = self.gateway_request_url(
            api_id=result['id'],
            stage_name=self.TEST_STAGE_NAME,
            path=self.API_PATH_DATA_INBOUND
        )
        result = requests.post(url, data=json.dumps(test_data))
        self.assertEqual(result.status_code, 200)
        messages = aws_stack.sqs_receive_message(self.TEST_SQS_QUEUE)['Messages']
        self.assertEqual(len(messages), 1)
        self.assertEqual(json.loads(base64.b64decode(messages[0]['Body'])), test_data)
    def test_api_gateway_http_integration(self):
        test_port = 12123
        backend_url = 'http://localhost:%s%s' % (test_port, self.API_PATH_HTTP_BACKEND)
        
        class TestListener(ProxyListener):