Clean up initTestingHarnessWaitUntilDone

initTestingHarnessWaitUntilDone() did not differ functionally from
initTestingHarness(), which is usually called through description(). In
addition some tests that are in fact asynchronous (for example using
setTimeout) are missing initTestingHarnessWaitUntilDone calls. Rely on
description() to always call the platform test harness waitUntilDone
function, and remove redundant calls.