Creating valid XML HTTP response example code bug

The example code has 2 bugs:
1: it has extra slashes and double quotes surrounding the status attribute
2: it does not create a valid XML HTTP response, instead it creates a simple text/plain response containing a headless xml string.

I removed the extra quotes and slashes and I put the right content-type to the result.
There could be a better version adding: ```<?xml version=\"1.0\" encoding=\"UTF-8\"?>``` before every <message> tag.