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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)

...

if key_file_name:
            kwargs['keyfile'] = key_file_name
            config.keyfile = key_file_name
        setup_quart_logging()
        config.bind = ['0.0.0.0:%s' % port]
        loop = loop or ensure_event_loop()
        run_kwargs = {}
        if shutdown_event:
            run_kwargs['shutdown_trigger'] = shutdown_event.wait
        try:
            try:
                return loop.run_until_complete(serve(app, config, **run_kwargs))
            except Exception as e:
                LOG.info('Error running server event loop on port %s: %s %s' % (port, e, traceback.format_exc()))
                if 'SSL' in str(e):
                    c_exists = os.path.exists(cert_file_name)
                    k_exists = os.path.exists(key_file_name)
                    c_size = len(load_file(cert_file_name)) if c_exists else 0
                    k_size = len(load_file(key_file_name)) if k_exists else 0
                    LOG.warning('Unable to create SSL context. Cert files exist: %s %s (%sB), %s %s (%sB)' %
                                (cert_file_name, c_exists, c_size, key_file_name, k_exists, k_size))
                raise
        finally:
            try:
                _cancel_all_tasks(loop)
                loop.run_until_complete(loop.shutdown_asyncgens())
            finally:
                asyncio.set_event_loop(None)
                loop.close()
    class ProxyThread(FuncThread):