Fixes infinite loop in start_mqtt_async - hummingbot/brokers/issues/8

[klpanagi]

Before submitting this PR, please make sure:

• Your code builds clean without any errors or warnings
• You are using approved title ("feat/", "fix/", "docs/", "refactor/")

A description of the changes proposed in the pull request:

Fixes errors produced while using the mqtt_autostart. Reported in: hummingbot/brokers/issues/8#issuecomment-1846971660

Tests performed by the developer:

Tested 2 Cases.

Case 1 - mqtt_autostart enabled on startup:

• Broker is disconnected
• Start the bot
• Import a strategy
• Start the strategy
• Start the broker
• Bot should connect successfully and without any disconnection logs

Case 2 - mqtt_autostart disabled on startup:

• Broker is disconnected
• Start the bot
• Set the mqtt_autostart to True
• Connect to broker
• Import a strategy
• Start the strategy
• Start the broker
• Bot should connect successfully and without any disconnection logs

And of course I have tested while the broker is running before starting the bot

Tips for QA testing:

[david-hummingbot]

• Built Docker image and tested using Dashboard
• Master Bot is able to reconnect without restarting container when broker is started

[cardosofede]

LGTM!

[rapcmia]

Merged to development and part of release version 1.23.0