testee does not exit if using a config

On all of our projects that are now on CanJS5/DoneJS3 testee no longer exits on completion of tests.

I've setup a bone stock donejs3 app with the only modification being the use of a config file for tests. The single tests completes successfully but testee does not exit.

https://github.com/tracer99/testee-exit

Platforms tested:
NodeJS 8 through 12
Debian Stable & old-stable
WSL & WSL2 (Debian Stable)
OSX

Note: The tests for testee itself exhibit this exact issue.

Start with the linked testee-exit reproduction and the testee project's own tests, which reportedly show the same behavior when a config file is used. Run the configured single-test case and trace why the process remains alive; done means testee exits after the tests complete successfully.

Written by the indexing model from the issue text.