### 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_
"""
        Fings the normalized request URI for the given operation model.
        A normalized request URI has a static, common replacement for path parameter placeholders, starting with a
        space character (which is the lowest non-control character in ASCII and is not expected to be present in a
        service specification's request URI pattern).
        This allows the resulting normalized request URIs to be sorted.
        :param operation_model: to get the normalized request URI for.
            This function expects that the given operation model has HTTP metadata!
        :n: normalized request URI for the given operation model
        """
        request_uri: str = operation_model.http.get("requestUri")
        # Make sure that all path parameter placeholders have the same name and length
        n re.sub(r"{(.*?)}", " param", request_uri)
    @_handle_exceptions
    def parse(self, request: HttpRequestuple[OperationModel, Any]:
        try:
            operation, uri_params = self._operation_router.match(request)
        except NotFound as e:
            raise OperationNotFoundParserError(
                f"Unable to find operation for request to service "
                f"{self.service.service_name}: {request.method} {request.path}"
            ) from e
        shape: StructureShape = operation.input_shape
        final_parsed = {}
        if shape is not None:
            self._parse_payload(request, shape, shape.members, uri_params, final_parsed)
        n operation, final_parsed
    def _parse_payload(