test_multiple_clusters_simultaneously_same_loop hangs frequently in CI

[jacobtomlinson]

The test_multiple_clusters_simultaneously_same_loop is flaky and hangs around 10% of the time.

https://github.com/dask/dask-kubernetes/actions/runs/3461240518/jobs/5778594809
https://github.com/dask/dask-kubernetes/actions/runs/3461240518/jobs/5778594528
https://github.com/dask/dask-kubernetes/actions/runs/3461266262/jobs/5778653244

I've skipped it in #609 for now and opening this to track reinstating it.

@graingert, as you wrote this test would you be able to take a look?