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. 
bucket_name = 'test-%s' % short_uid()
        self.s3_client.create_bucket(Bucket=bucket_name)
        
        object_key = 'key-with-metadata'
        metadata = {'test_meta_1': 'foo', '__meta_2': 'bar'}
        self.s3_client.put_object(Bucket=bucket_name, Key=object_key, Metadata=metadata, Body='foo')
        metadata_saved = self.s3_client.head_object(Bucket=bucket_name, Key=object_key)['Metadata']
        self.assertEqual(metadata, metadata_saved)
        
        self._delete_bucket(bucket_name, [object_key])
    def test_range_header_body_length(self):
        
        object_key = 'sample.bin'
        bucket_name = 'test-%s' % short_uid()
        self.s3_client.create_bucket(Bucket=bucket_name)
        chunk_size = 1024
        with io.BytesIO() as data:
            data.write(os.urandom(chunk_size * 2))
            data.seek(0)
            self.s3_client.upload_fileobj(data, bucket_name, object_key)
        range_header = 'bytes=0-%s' % (chunk_size - 1)
        resp = self.s3_client.get_object(Bucket=bucket_name, Key=object_key, Range=range_header)
        content = resp['Body'].read()
        self.assertEquals(len(content), chunk_size)
        
        self._delete_bucket(bucket_name, [object_key])
    def test_s3_get_response_content_type_same_as_upload_and_range(self):