Removed reliance on worker exit before arbitrary timeout. Instead of killing
the parent process, destroy the IPC pipe for the same effect, and wait for
the worker's exit before also exiting the parent. Insuring these steps are
well-ordered removes the need for timeouts and reduces intermittent failures.

In case of an actual hang in the child's exit code, the test harness global
timeout will kick in, and the test will still fail.