U.S. RESEARCH ROUNDUP-Weatherford, General Motors, Endo International

May 6 (Reuters) - Wall Street securities analysts revised their ratings and price targets on several U.S.-listed companies, including Total System Services, Ubiquiti Networks and Advance Auto Parts, on Friday. HIGHLIGHTS * United Rentals Inc : Goldman Sachs cuts to sell from neutral * Weatherford International : Seaport Global Securities raises to buy from neutral * Endo International Plc : Mizuho Securities cuts to underperform from neutra