If fCBISHangBeforeFinish is interrupted by cancelation (e.g. at shutdown), we will uassert out of _finishCallback and be left in a state where _onCompletion is nullptr and _state is not State::kComplete. The state will cause us to call _finishCallback again, at which point it will crash because of _onCompletion being null. Instead we should swallow the "interrupted" exception and just continue when fCBISHangBeforeFinish is interrupted.