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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)

...

lambda_client.create_event_source_mapping(EventSourceArn=queue_arn2, FunctionName=lambda_name)
        
        payload = {
            lambda_integration.MSG_BODY_RAISE_ERROR_FLAG: 1
        }
        self.client.send_message(QueueUrl=queue_url2, MessageBody=json.dumps(payload))
        
        def receive_dlq():
            result = self.client.receive_message(QueueUrl=queue_url1, MessageAttributeNames=['All'])
            self.assertGreater(len(result['Messages']), 0)
            msg_attrs = result['Messages'][0]['MessageAttributes']
            self.assertIn('RequestID', msg_attrs)
            self.assertIn('ErrorCode', msg_attrs)
            self.assertIn('ErrorMessage', msg_attrs)
        retry(receive_dlq, retries=8, sleep=2)
    def test_set_queue_attribute_at_creation(self):
        queue_name = 'queue-%s' % short_uid()
        attributes = {
            'MessageRetentionPeriod': '604800',  
            'ReceiveMessageWaitTimeSeconds': '10',
            'VisibilityTimeout': '30'
        }
        queue_url = self.client.create_queue(QueueName=queue_name, Attributes=attributes)['QueueUrl']
        creation_attributes = self.client.get_queue_attributes(QueueUrl=queue_url, AttributeNames=['All'])
        
        self.assertIn('MessageRetentionPeriod', creation_attributes['Attributes'].keys())
        self.assertEqual('604800', creation_attributes['Attributes']['MessageRetentionPeriod'])
        
        self.client.delete_queue(QueueUrl=queue_url)
    def test_get_specific_queue_attribute_response(self):