MQTT Device is prepended to the name of registered MQTT devices in some cases

[Bravo555]

Describe the bug

A string MQTT Device can be prepended to the name of some devices in Cumulocity when using thin-edge.io:

MQTT Device is prepended by Cumulocity 1 if publishing on a topic for a device that was not registered.
Can be manually triggered by publishing a message like: tedge mqtt pub c8y/s/us/my_device 101,myChildDevice,myType
If my_device registration message is not sent beforehand, MQTT Device my_device is automatically registered.

This bug can sometimes happen in thin-edge due to random order of c8y registration messages being sent when e.g. reconnecting to the broker if the device was deleted from the broker.

To Reproduce

The bug is difficult to reproduce with thin-edge because it's somewhat random. If a consistent method is found it will be placed here.

Expected behavior

Device names should never be prepended with MQTT Device; locally we know full names and types of entities before sending any messages to the cloud so we should explicitly register a device before sending any messages.

Screenshots

Environment (please complete the following information):

• OS [incl. version]
• Hardware [incl. revision]
• System-Architecture [e.g. result of "uname -a"]
• thin-edge.io version [e.g. 0.1.0]

Additional context