BEIJING, July 15 (Reuters) - Chinese President Xi Jinping said China must build a "solid" security barrier around its internet under the supervision of the ruling Communist Party, in his latest call to safeguard online data and information. China must persist in managing, operating and ensuring access to the internet in accordance with the law, Xi said in instructions delivered to officials attending a two-day cybersecurity meeting in Beijing that ended on Saturday. "We must adhere to the Party's management of the internet and adhere to (the principle of) making the internet work for the people," state-run Xinhua news agency...