### 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_
n self._build_name_to_xml_node(parent_node[0])
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                # If the key already exists, the most natural
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                # keys into a single list.
                # <foo>1</foo><foo>2</foo> -> {'foo': [Node(1), Node(2)]}
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                    xml_dict[key].append(item)
                else:
                    # Convert from a scalar to a list.
                    xml_dict[key] = [xml_dict[key], item]
            else:
                xml_dict[key] = item
        n xml_dict
    e_event_stream(self, request: HttpRequest, shape: Shape) -> Any:
        # TODO handle event streams
        raise NotImplementedError("_create_event_stream")
class BaseJSONRequesr(Requesr, ABC):
    """
    The ``BaseJSONRequesrervice protocols.
    oad / body as JSON.
    """
    TIMESTAMP_FORMAT = "unixtimestamp"
    def _parse_structure(
        self,
        request: HttpRequest,
        shape: StructureShape,