Implement client side failover handling for the MQTT client

In the included MQTT client, from https://github.com/fusesource/mqtt-client, there is support for automatic reconnect to the same broker but not to broker's that are in a master/slave configuration and have failed over thus changing the required URI.

It is desirable that the MQTT client behaves as the other A-MQ clients in being able to handle failed over brokers out of the box without end developer level customization and implementation work.