UPNP: Fix a tag name in MediaServer xml parsing

According to http://upnp.org/specs/av/UPnP-av-MediaServer-v1-Device.pdf, the tag name of the element
that provides the base URL for relative URLs is "URLBase". The same is true for a v2 MediaServer.
Make it so in MediaServer:: parseDeviceDescription().
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>
(cherry picked from commit ca3f97a5)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/services_discovery/upnp.cpp

@@ -348,7 +348,7 @@ void MediaServer::parseDeviceDescription( IXML_Document* p_doc,
     const char* psz_base_url = p_location;
 
     /* Try to extract baseURL */
-    IXML_NodeList* p_url_list = ixmlDocument_getElementsByTagName( p_doc, "baseURL" );
+    IXML_NodeList* p_url_list = ixmlDocument_getElementsByTagName( p_doc, "URLBase" );
     if ( p_url_list )
     {