upnpsoap: fix incorrectly formed Samsung GetFeatureList reply

Bug raised here https://sourceforge.net/p/minidlna/bugs/210/, and also
mentioned in http://sourceforge.net/p/minidlna/discussion/879956/thread/34276163/.
However patch given needs to correctly escaped to work otherwise the
renderer will get stuck in an endless loop.

Signed-off-by: Spencer Oliver <spen@spen-soft.co.uk>