Add command to let the cli fuzz an MQTT broker

[MicWalter]

Problem or use case

A maintainer/developer of an MQTT broker might want to fuzz his broker to find possible decoding/implementation issues.

Preferred solution or suggestions

The command could be: mqtt fuzz [-h brokerHost -p brokerPort]

Open questions:

• Check if an existing mqtt fuzzer can be used or if a custom fuzzer has to be implemented.
• Should additional commands be supplied that allow to increase/decrease duration of fuzzing?