Fix flaky test_exit_callback

[crusaderky]

No description provided.

[github-actions]

Unit Test Results

See test report for an extended history of previous test failures. This is useful for diagnosing flaky tests.

   19 files   -     21     19 suites   - 21   2h 57m 18s ⏱️ - 12h 3m 4s
  500 tests  -  3 654    500 ✅  -  3 475  0 💤  -   178  0 ❌  - 1 
9 500 runs   - 71 341  9 500 ✅  - 67 103  0 💤  - 4 237  0 ❌  - 1 

Results for commit 71afe5a. ± Comparison against base commit ace5560.

This pull request removes 4154 and adds 500 tests. Note that renamed tests count towards both.

distributed.cli.tests.test_dask_scheduler ‑ test_dashboard
distributed.cli.tests.test_dask_scheduler ‑ test_dashboard_allowlist
distributed.cli.tests.test_dask_scheduler ‑ test_dashboard_non_standard_ports
distributed.cli.tests.test_dask_scheduler ‑ test_dashboard_port_zero
distributed.cli.tests.test_dask_scheduler ‑ test_defaults
distributed.cli.tests.test_dask_scheduler ‑ test_hostport
distributed.cli.tests.test_dask_scheduler ‑ test_idle_timeout
distributed.cli.tests.test_dask_scheduler ‑ test_interface
distributed.cli.tests.test_dask_scheduler ‑ test_multiple_protocols
distributed.cli.tests.test_dask_scheduler ‑ test_multiple_workers
…

distributed.tests.test_asyncprocess ‑ test_exit_callback[1-500]
distributed.tests.test_asyncprocess ‑ test_exit_callback[10-500]
distributed.tests.test_asyncprocess ‑ test_exit_callback[100-500]
distributed.tests.test_asyncprocess ‑ test_exit_callback[101-500]
distributed.tests.test_asyncprocess ‑ test_exit_callback[102-500]
distributed.tests.test_asyncprocess ‑ test_exit_callback[103-500]
distributed.tests.test_asyncprocess ‑ test_exit_callback[104-500]
distributed.tests.test_asyncprocess ‑ test_exit_callback[105-500]
distributed.tests.test_asyncprocess ‑ test_exit_callback[106-500]
distributed.tests.test_asyncprocess ‑ test_exit_callback[107-500]
…