With Vice President Kamala Harris poised as a likely replacement for Joe Biden on the Democratic presidential ticket, White House aides are raising alarm about the VP once labeled a “boss from hell,” RadarOnline.com has learned. Biden, 81, endorsed his second-in-command as he bowed out of the race on Sunday, giving in to the growing fear that he would be unable to beat GOP candidate Donald Trump in November. But as Harris, 59, launched her campaign this week, concerns about the reportedly high turnover under her leadership were back in the spotlight. Axios spoke with three staffers who said Bi…