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
```
self.assertEqual(content['data'], data)
        self.assertEqual(headers['content-type'], ctype)
        
        proxy.stop()
    def test_api_gateway_lambda_proxy_integration(self):
        self._test_api_gateway_lambda_proxy_integration(
            self.TEST_LAMBDA_PROXY_BACKEND,
            self.API_PATH_LAMBDA_PROXY_BACKEND)
    def test_api_gateway_lambda_proxy_integration_with_path_param(self):
        self._test_api_gateway_lambda_proxy_integration(
            self.TEST_LAMBDA_PROXY_BACKEND_WITH_PATH_PARAM,
            self.API_PATH_LAMBDA_PROXY_BACKEND_WITH_PATH_PARAM)
    def _test_api_gateway_lambda_proxy_integration(self, fn_name, path):
        self.create_lambda_function(fn_name)
        
        lambda_uri = aws_stack.lambda_function_arn(fn_name)
        invocation_uri = 'arn:aws:apigateway:%s:lambda:path/2015-03-31/functions/%s/invocations'
        target_uri = invocation_uri % (config.DEFAULT_REGION, lambda_uri)
        result = self.connect_api_gateway_to_http_with_lambda_proxy(
            'test_gateway2', target_uri, path=path)
        api_id = result['id']
        path_map = get_rest_api_paths(api_id)
        _, resource = get_resource_for_path('/lambda/foo1', path_map)
        
        path = path.replace('{test_param1}', 'foo1')
        path = path + '?foo=foo&bar=bar&bar=baz'
        url = self.gateway_request_url(
            api_id=api_id, stage_name=self.TEST_STAGE_NAME, path=path)
        data = {'return_status_code': 203, 'return_headers': {'foo': 'bar123'}}
        result = requests.post(url, data=json.dumps(data),