[BUG] Dbus Event handler keeps publishing data even on unsuccessful connections

[PFigs]

Describe the bug
The transport service keeps receiving DBUS packets and calling received_data even when a MQTT connection is not established correctly.

I've observed that sometimes the transport service exits cleanly as expected.

To Reproduce
Steps to reproduce the behavior:

1. Configure incorrect user/pwd credentials
2. Start the gateway services

Expected behavior
The transport service should exit

Platform details:

• OS: Ubuntu 19.04
• Gateway host: x86_64 desktop
• Python version: 3.6
• Docker engine: 18.06.1-ce
• MQTT Broker vendor: mosquitto
• MQTT Broker version: 1.6