[Fix] Python xbmcvfs.listdir(url) not returning upnp address folder data.

...if it's an upnp://[address], and calling the XFILE::CDirectoryFactory::Create() method to create the CUPnPDirectory class object.

This will allow the python method in xbmcvfs.listdir() method to return upnp data. This check-in is required for an add-on I'm working on extending the tv-guide addon for hdhomerun devices.