### 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_
@staticmethod
    def _member_key_name(shape: Shape, member_name: str) -> str:
        # This method is needed because we have to special case flattened list
        # with a ization name.  If this is the case we use the
        # locationName from the list's member shape as the key name for the
        # surrounding structure.
        ened"):
            t("name")
            if list_memberlized_name is not None:
                n list_memberlized_name
        ized_name = shape.ization.get("name")
        if ized_name is not None:
            n ized_name
        n member_name
    @staticmethod
    def _parse_xml_string_to_dom(xml_string: str) -> ETree.Element:
        try:
            parser = ETree.XMLParser(target=ETree.TreeBuilder())
            parser.feed(xml_string)
            root = parser.close()
        except ETree.ParseError as e:
            raise ProtocolParserError(
                "Unable to parse re received:\n%s" % (e, xml_string)
            ) from e
        n root
    def _build_name_to_xml_node(self, parent_node: Union[list, ETree.Element]) -> dict:
        # If the parent node is actually a list. We should not be trying
        # to ize it to a dictionary. Instead, n the first element
        # in the list.
        if isinstance(parent_node, list):