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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)

...

queue_name = 'queue-{}'.format(short_uid())
        queue_url = self.client.create_queue(QueueName=queue_name)['QueueUrl']
        number_of_messages = 3
        for i in range(number_of_messages):
            self.client.send_message(
                QueueUrl=queue_url,
                MessageBody='hello world. {}'.format(i),
                DelaySeconds=0
            )
        messages = {}
        for i in range(number_of_messages):
            rs = self.client.receive_message(QueueUrl=queue_url)
            m = rs['Messages'][0]
            messages[m['MessageId']] = m['Body']
        self.assertEqual(len(messages.keys()), number_of_messages)
        
        self.client.delete_queue(QueueUrl=queue_url)
    def test_lambda_invoked_by_sqs_message_with_delay_seconds(self):
        function_name = 'lambda_func-{}'.format(short_uid())
        queue_name = 'queue-{}'.format(short_uid())
        delay_time = 6
        queue_url = self.client.create_queue(QueueName=queue_name)['QueueUrl']
        queue_arn = aws_stack.sqs_queue_arn(queue_name)
        testutil.create_lambda_function(
            handler_file=TEST_LAMBDA_ECHO_FILE,
            func_name=function_name,
            runtime=LAMBDA_RUNTIME_PYTHON36
        )
        lambda_client = aws_stack.connect_to_service('lambda')