update the root (aka SystemUpdateId) when we update ours... The

PS3 asks for this a lot, so I figure we should update it now..

[git-p4: depot-paths = "//depot/": change = 1107]

DIDLLite.py

@@ -275,6 +275,7 @@ class Container(Object, list):
 
 	def doUpdate(self):
 		self.updateID = (self.updateID + 1) % (1l << 32)
+		self.cd['0'].doUpdate()
 
 	def toElement(self):