Reconnection loop when device is disconnected by Astarte

[Annopaolo]

#22 relies on the assumption that after the first connection, a MQTT session for the device is always present, as we never ask for a clean session.
However, the assumption does not hold when Astarte disconnects the device. In that case, the current automatic reconnection mechanism does not perform the required Astarte MQTT v1 steps (publishing introspection/emptycache/properties), and so the device enters a reconnection loop.
Relevant SDK logs using the example code:

Received error: EOF
Device connection state: false
Sending old messages with non-discard retention
Device connection state: true
Sending old messages with non-discard retention
Received error: EOF
Device connection state: false
Sending old messages with non-discard retention
Device connection state: true
Sending old messages with non-discard retention
Received error: EOF
...