Hi!

I have noticed that today (25th of Feb) a new version of localstack docker image was pushed to the repository (82c83ff027114060938856eac5dc7be1d534afd0b7711510246de4a76dde2396) and this version fails in my integration tests with an exception:

```
2020-02-25T12:09:44:ERROR:localstack.services.generic_proxy: Error forwarding request: An error occurred (404) when calling the HeadObject operation: Not Found Traceback (most recent call last):
  File "/opt/code/localstack/localstack/services/generic_proxy.py", line 303, in forward updated_response = self.proxy.update_listener.return_response(**kwargs)
  File "/opt/code/localstack/localstack/services/s3/s3_listener.py", line 954, in return_response
send_notifications(method, bucket_name, object_path, version_id)
  File "/opt/code/localstack/localstack/services/s3/s3_listener.py", line 178, in send_notifications
send_notification_for_subscriber(notif, bucket_name, object_path,
  File "/opt/code/localstack/localstack/services/s3/s3_listener.py", line 191, in send_notification_for_subscriber
object_size = s3_client.head_object(Bucket=bucket_name, Key=key).get('ContentLength', 0)
  File "/opt/code/localstack/.venv/lib/python3.8/site-packages/botocore/client.py", line 316, in _api_call
return self._make_api_call(operation_name, kwargs)
  File "/opt/code/localstack/.venv/lib/python3.8/site-packages/botocore/client.py", line 626, in _make_api_call
  raise error_class(parsed_response, operation_name)
botocore.exceptions.ClientError: An error occurred (404) when calling the HeadObject operation: Not Found
```
The same setup in docker-compose works with version 0.10.7 and 0.10.6 without any errors or exceptions. 
key_by_path = 'aws/bucket0/test1'
        queue_url, queue_attributes = self._create_test_queue()
        self._create_test_notification_bucket(queue_attributes)
        self.s3_client.put_bucket_versioning(Bucket=TEST_BUCKET_WITH_NOTIFICATION,
                                             VersioningConfiguration={'Status': 'Enabled'})
        
        body = """ Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Aenean commodo ligula eget dolor. 
        Aenean massa. Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. 
        Donec quam felis, ultricies nec, pellentesque eu, pretium quis, sem. Nulla consequat massa quis enim. 
        Donec pede justo, fringilla vel, aliquet nec, vulputate eget, arcu. In enim justo, rhoncus ut, imperdiet a,. 
        Nullam dictum felis eu pede mollis pretium. Integer tincidunt. Cras dapibus. Vivamus elementum semper nisi. 
        Aenean vulputate eleifend tellus. Aenean leo ligula, porttitor eu, consequat vitae, eleifend ac, enim. 
        Aliquam lorem ante, dapibus in, viverra quis, feugiat a, tellus. Phasellus viverra nulla ut metus varius laoreet. 
        Quisque rutrum. Aenean imperdiet. Etiam ultricies nisi vel augue. Curabitur ullamcorper ultricies nisi. Nam eget dui. 
        Etiam rhoncus. Maecenas tempus, tellus eget condimentum rhoncus, sem quam semper libero, sed ipsum. """
        
        self.s3_client.put_object(Bucket=TEST_BUCKET_WITH_NOTIFICATION, Key=key_by_path, Body=body)
        self.assertEqual(self._get_test_queue_message_count(queue_url), '1')
        rs = self.sqs_client.receive_message(QueueUrl=queue_url)
        record = [json.loads(to_str(m['Body'])) for m in rs['Messages']][0]['Records'][0]
        download_file = new_tmp_file()
        self.s3_client.download_file(Bucket=TEST_BUCKET_WITH_NOTIFICATION,
                                     Key=key_by_path, Filename=download_file)
        self.assertEqual(record['s3']['object']['size'], os.path.getsize(download_file))
        
        self.s3_client.put_bucket_versioning(Bucket=TEST_BUCKET_WITH_NOTIFICATION,
                                             VersioningConfiguration={'Status': 'Disabled'})
        self.sqs_client.delete_queue(QueueUrl=queue_url)
        self._delete_bucket(TEST_BUCKET_WITH_NOTIFICATION, [key_by_path])
    def test_s3_delete_object_with_version_id(self):