Update XmlReporter to XML encode attribute strings

Avoids problem where filename or description contains illegal XML
characters (like an ampersand) by escaping the output.

Change-Id: I161de23cd8d52d5b8bab540457fd5fcb4d44add9
Reviewed-on: http://gerrit.causes.com/37215
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>