CI tests are flaky

[jarl-dk]

Example is these two runs on exactly the same git sha:
Fails:
https://app.circleci.com/pipelines/github/mountebank-testing/mountebank/1140/workflows/fbb2e733-3a07-45d2-ad1f-728cdb77b457
Pass:
https://app.circleci.com/pipelines/github/mountebank-testing/mountebank/1140/workflows/014bbf1b-babd-4393-a0c1-3baa5f5c214a