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# Type of request: This is a ...

[x] bug report
[ ] feature request

# Detailed description

In the `ReceiveMessageResult` of the SQS service, I saw this XML from localstack:

```
...
<MessageAttribute>
     <Name>encoding</Name>
    <Value>
        <DataType>String</DataType>
        <StringValue><![CDATA[gzip]]></StringValue>
    </Value>
</MessageAttribute>
...
```

The `<![CDATA[gzip]]>` is slightly different from AWS, which doesn't wrap the value in a `<!CDATA[[]]>` section. This shouldn't be a problem for XML parsers that accept both plain characters and CDATA sections for this element, but the XML parser I was using did not, which causes an error when running the code against localstack but not when running the code against AWS. There is obviously a bug in the XML parser as well, but I thought that I should at least post this here since it is different than what AWS SQS does.

## Expected behavior

MessageAttribute::Value elements should not be wrapped in `CDATA` sections.

## Actual behavior

MessageAttribute::Value elements all seem to be wrapped in `CDATA` sections.

# Steps to reproduce

Send a message to the SQS service which contains some custom message attributes, then make a ReceiveMessageRequest.

## Command used to start LocalStack

`docker run --env "SERVICES=sqs" localstack/localstack`

## Client code (AWS SDK code snippet, or sequence of "awslocal" commands)

...

{'Id': '{:02d}'.format(i), 'ReceiptHandle': m['ReceiptHandle']}
                for i, m in enumerate(messages)
            ]
        )
        response = receive_messages()
        self.assertFalse(response.get('Messages'))
        
        self.client.send_message_batch(QueueUrl=queue_url, Entries=messages_to_send)
        messages = receive_messages()['Messages']
        response = receive_messages()
        self.assertFalse(response.get('Messages'))
        reset_hashes = get_hashes(messages[:5])
        self.client.change_message_visibility_batch(
            QueueUrl=queue_url,
            Entries=[
                {
                    'Id': '{:02d}'.format(i),
                    'ReceiptHandle': msg['ReceiptHandle'],
                    'VisibilityTimeout': 0,
                }
                for i, msg in enumerate(messages[:5])
            ]
        )
        for i in range(2):
            messages = receive_messages(VisibilityTimeout=0)['Messages']
            received_hashes = get_hashes(messages)
            self.assertEqual(reset_hashes, received_hashes)
        
        self.client.delete_queue(QueueUrl=queue_url)
    def test_create_fifo_queue(self):