hang up connection after relaying

Seems that git upload-pack outputs a "ONCDN " that is not read by the
remote git receive-pack. This fixes:

[2016-12-09 17:08:32.77159731] P2P > ERROR protocol parse error: "ONCDN "

P2P/Protocol.hs

@@ -387,7 +387,10 @@ serveAuthed myuuid = void $ serverLoop handler
 		return ServerContinue
 	handler (CONNECT service) = do
 		net $ relayService service
-		return ServerContinue
+		-- After connecting to git, there may be unconsumed data
+		-- from the git processes hanging around (even if they
+		-- exited successfully), so stop serving this connection.
+		return $ ServerGot ()
 	handler NOTIFYCHANGE = do
 		refs <- local waitRefChange
 		net $ sendMessage (CHANGED refs)