MQTT: Implements reconnecting in publish thread in case thread is waken-up but client is disconnected.

Note: paho's lostConnection callback got already disabled in previous commit.

<?xml version='1.0' encoding='utf-8'?>
<BeremizRoot xmlns:xsd="http://www.w3.org/2001/XMLSchema" URI_location="LOCAL://">
  <TargetType/>
</BeremizRoot>