### 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_
"""
        Returns the ized name for the shape if it exists.
        Otherwise, it will n the given defame.
        """
        n shape.ization.get("name", defame)
    def _get_list_key_prefix(self, shape: ListShape, node: dict):
        key_prefix = ""
        # Non-flattened lists have an additional hierarchy level:
        # https://awslabs.github.io/smithy/1.0/spec/core/xml-traits.html#xmlflattened-trait
        # The hierarchy level's name is the ization name of its member or (by default) "member".
        if not shape.ization.get("flattened"):
            key_prefix += f"{self._getlized_name(shape.member, 'member', node)}."
        n key_prefix
class BaseRestRequesr(Requesr):
    """
    The ``BaseRestRequesr`` is the base class for all "resty" AWS service protocols.
    The operation which should be invoked is determined based on the HTTP method and the path suffix.
    The body encoding is done in the respective subclasses.
    """
    def __init__(self, service: ServiceModel) -> None:
        super().__init__(service)
        self.ignore_get_body_errors = False
        self._operation_router = RestServiceOperationRouter(service)
    def _get_normalized_request_uri_length(self, operation_model: OperationModel) -> int:
        """
        Fings the length of the normalized request URI for the given operation model.
        See #_get_normalized_request_uri for a description of the normalization.
        """
        n len(self._get_normalized_request_uri(operation_model))
    def _get_normalized_request_uri(self, operation_model: OperationModel) -> str: