### 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_
"""
    Basic test for the QueryParser with a simple example (SQS SendMessage request),
    where the parameters are encoded in the URI instead of the body.
    """
    parser = QueryRequestParser(load_service("sqs"))
    request = HttpRequest(
        query_string="Action=SendMessage&Version=2012-11-05&"
        "QueueUrl=http%3A%2F%2Flocalhost%3A4566%2F000000000000%2Ftf-acc-test-queue&"
        "MessageBody=%7B%22foo%22%3A+%22bared%22%7D&"
        "DelaySeconds=2",
        method="POST",
        path="",
    )
    operation, params = parser.parse(request)
    assert operation.name == "SendMessage"
    assert params == {
        "QueueUrl": "http://localhost:4566/000000000000/tf-acc-test-queue",
        "MessageBody": '{"foo": "bared"}',
        "DelaySeconds": 2,
    }
def test_query_parser_flattened_map():
    """Simple test with a flattened map (SQS SetQueueAttributes request)."""
    parser = QueryRequestParser(load_service("sqs"))
    request = HttpRequest(
        body=to_bytes(
            "Action=SetQueueAttributes&Version=2012-11-05&"
            "QueueUrl=http%3A%2F%2Flocalhost%3A4566%2F000000000000%2Ftf-acc-test-queue&"