quotest occasionally gets stuck after completing all tests

[KitsuneRal]

The internal watchdog force-finishes it but it would be great to fix that.

[KitsuneRal]

Aside from overlapping quotest runs, quotest may get stuck when rate-limiting occurs. It's not quite clear what is happening but it's pretty clear that waiting for messageSent() and checking pending messages is not the most reliable way to track the sending queue expiry. Queueing events should definitely help (and further reduce the amount of server-driven rate-limiting).