### 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_
"ChangeSetName=SampleChangeSet&"
            "Parameters.member.1.ParameterKey=KeyName&"
            "Parameters.member.1.UsePreviousValue=true&"
            "Parameters.member.2.ParameterKey=Purpose&"
            "Parameters.member.2.ParameterValue=production&"
            "StackName=arn:aws:cloudformation:us-east-1:123456789012:stack/SampleStack/1a2345b6-0000-00a0-a123-00abc0abc000&"
            "UsePreviousTemplate=true&"
            "Version=2010-05-15&"
            "X-Amz-Algorithm=AWS4-HMAC-SHA256&"
            "X-Amz-Credential=[Access-key-ID-and-scope]&"
            "X-Amz-Date=20160316T233349Z&"
            "X-Amz-SignedHeaders=content-type;host&"
            "X-Amz-Signature=[Signature]"
        ),
        method="POST",
        headers={"Content-Type": "application/x-www-form-urlencoded"},
        path="",
    )
    operation, params = parser.parse(request)
    assert operation.name == "CreateChangeSet"
    assert params == {
        "StackName": "arn:aws:cloudformation:us-east-1:123456789012:stack/SampleStack/1a2345b6-0000-00a0-a123-00abc0abc000",
        "UsePreviousTemplate": True,
        "Parameters": [
            {"ParameterKey": "KeyName", "UsePreviousValue": True},
            {"ParameterKey": "Purpose", "ParameterValue": "production"},
        ],
        "ChangeSetName": "SampleChangeSet",
    }
def test_query_parser_non_flattened_list_structure_changed_name():