By David Kirton SHANGHAI (Reuters) -Shanghai will remain under lockdown as it reviews results of an exercise to test all of its 26 million residents for COVID-19, authorities said on Monday. The city began its two-stage lockdown on March 28, initially in Shanghai’s eastern districts, and later expanded to cover the whole city. The curbs, which have massively disrupted daily life and business operations in China’s financial hub, were initially scheduled to end at 5 a.m. local time (9 p.m. GMT) on Tuesday. “The city will continue to implement seal and control management and strictly implement ‘s…