Courtney Ruby, 47, is no stranger to politics.  Now in her eighth year as Oakland’s elected city auditor, she’s entered a large crowd of candidates seeking to unseat incumbent Mayor Jean Quan. “I have proven leadership experience,” she said. “I’ve been under the hood of almost every department, I know what’s broken, and I have the skills to fix it. I have turned a troubled agency into performing model audit organization.” She is running on the promise of keeping public…