beremiz

089ecd14deb3
MQTT: Fix warning when subscribing first topic from python.

Ensure that message callback is already set before subscribing a topic from python.
<?xml version='1.0' encoding='utf-8'?>
<ModbusTCPclient xmlns:xsd="http://www.w3.org/2001/XMLSchema" Remote_Port_Number="1502" Configuration_Name="Modbus TCP Client 0.0"/>