[v6.d REVIEW] Fix race conditions in Lock::Async tests
[v6.d REVIEW] Fix race conditions in Lock::Async tests

Or at least, I'm 90% certain those are races, looking at the interface.

Orig: https://github.com/perl6/roast/commit/8b5e39093

dogbert17/roast,dogbert17/roast,perl6/roast