Ignoring testShouldDoNothingIfThereIsNothingToGoBackTo on HtmlUnitDriver.

Pretty sure that has been broken by either 169dba6ad4dd1cfefdbc388a3ca36a1a24f7604e or f31bcf5abb3f1eb7529ddc78b6f744700af2a39d (both authored by me).
I assume this isn't worth effort looking into (has to do with JavaScriptExecution). Correct me if I'm wrong.