### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

There is an issue with `get-object-attributes` command which results in below error always: 
`aws --endpoint-url=http://localhost:4566 s3api get-object-attributes --bucket s3mock --key 20.txt --object-attributes "ObjectSize"`
````

> Response:  Unable to parse response (syntax error: line 1, column 0), invalid XML received. Further retries may succeed:
b'98\n5\n'
````

### How are you starting LocalStack?

With a docker-compose file

### Steps To Reproduce

#### Using docker-compse.yaml to start localstack

docker-compse.yaml:

```
localstack:
    image: localstack/localstack:latest
    ports:
      - '4563-4599:4563-4599'
      - '8055:8080'
    environment:
      - SERVICES=s3
      - DEBUG=1
      - LS_LOG=error
      - DATA_DIR=/tmp/localstack/data
      - AWS_DEFAULT_REGION=eu-west-1
      # - EDGE_PORT=4566
    volumes:
      - "./.localstack:/tmp/localstack"
      - "/var/run/docker.sock:/var/run/docker.sock"
```

#### cli commands to reproduce the issue

1. Create a Bucket: `aws --endpoint-url=http://localhost:4566 s3 mb s3://s3mock`
2. Create an Object: `aws --endpoint-url=http://localhost:4566 s3 cp data/20.txt s3://s3mock`

File 20.txt content are 2-digit numbers separated by newline.

3. get-object-attributes for object 20.txt :
```

 aws --endpoint-url=http://localhost:4566 s3api get-object-attributes --bucket s3mock --key 20.txt --object-attributes "ObjectSize"

```
Results in error:

> Unable to parse response (syntax error: line 1, column 0), invalid XML received. Further retries may succeed:
b'98\n5\n'



### Environment

```markdown
- OS:Mac 12.x
- LocalStack:latest
- Node 14
```


### Anything else?

_No response_
self, request: HttpRequest, shape: Shape, node: Any, uri_params: Mapping[str, Any] = None
    ) -> Any:
        """
        Main parsing method which dynamically calls the parsing function for the specific shape.
        :param request: the complete HttpRequest
        :param shape: of the node
        :param node: the single part of the HTTP request to parse
        :param uri_params: the extracted URI path params
        :n: result of the parsing operation, the type depends on the shape
        """
        if shape is None:
            n None
        location = shape.ization.get("location")
        if location is not None:
            if location == "header":
                header_name = shape.ization.get("name")
                payload = request.headers.get(header_name)
            elif location == "headers":
                payload = self._parse_header_map(shape, request.headers)
                # shapes with the location trait "headers" only contain strings and are not further processed
                n payload
            elif location == "querystring":
                query_name = shape.ization.get("name")
                parsed_query = request.args
                if shape.type_name == "list":
                    payload = parsed_query.getlist(query_name)
                else:
                    payload = parsed_query.get(query_name)
            elif location == "uri":
                uri_param_name = shape.ization.get("name")