Send MQTT heartbeat immediately after connection

CHANGELOG_LATEST.md

@@ -41,3 +41,4 @@
 - small changes to the API for analog and temperature sensors
 - Length of mqtt Broker adress [#1619](https://github.com/emsesp/EMS-ESP32/issues/1619)
 - C++ optimizations - see <https://github.com/emsesp/EMS-ESP32/pull/1615>
+- Send MQTT heartbeat immediately after connection

src/mqtt.cpp

@@ -508,7 +508,7 @@ void Mqtt::on_connect() {
     resubscribe();
 
     // publish to the last will topic (see Mqtt::start() function) to say we're alive
-    queue_publish_retain("status", "online", true); // with retain on
+    queue_publish_retain("status", "online", false); // with retain off
 
     // mqtt_publish_fails_ = 0; // reset fail count to 0
 }