Use higher-level disconnect function for opcua client

RCUSCC/RCUSCC/RCUSCC.py

@@ -415,8 +415,7 @@ class RCUSCC(Device):
     def _disconnect(self):
         try:
             if self.client is not None:
-                self.client.close_session()
-                self.client.close_secure_channel()
+                self.client.disconnect()
         except Exception as e:
             self.warn_stream("Disconnect from OPC-UA server %s:%d failed.  Trace: %s" % (self.OPC_Server_Name, self.OPC_Server_Port, traceback.format_exc()))
         finally: