Improve MQTT connection handling (#1462)

* modify mqtt init at startup + after disconnection

* mqtt_init only when not initialized

* Minor udapte

* Apply suggestions from code review

Co-authored-by: CaCO3 <caco3@ruinelli.ch>

* Correct typo

Co-authored-by: CaCO3 <caco3@ruinelli.ch>

code/components/jomjol_flowcontroll/ClassFlowControll.h

@@ -71,6 +71,7 @@ public:
 
 	t_CNNType GetTypeDigital();
 	t_CNNType GetTypeAnalog();
+	bool StartMQTTService();
 
 	int CleanTempFolder();