Unit Tests don't clean up docker containers

Description
===========

If you run a unit test over and over the number of stopped containers in Docker just piles up.

How to reproduce
================

Run the unit tests for this project, or even target a specific one and run it multiple times. It uses trivup to launch, but doesn't seem to cleanup after itself. I'm manually deleting the containers from Docker Desktop after a round of testing.

Checklist
=========
Please provide the following information:

- [] confluent-kafka-python and librdkafka version (`confluent_kafka.version()` and `confluent_kafka.libversion()`):
- [ ] Apache Kafka broker version:
- [ ] Client configuration: `{...}`
- [ ] Operating system:
- [ ] Provide client logs (with `'debug': '..'` as necessary)
- [ ] Provide broker log excerpts
- [ ] Critical issue