By Yew Lun Tian and Emma Farge BEIJING/GENEVA (Reuters) – The United Nations High Commissioner for Human Rights Michelle Bachelet begins a visit to China on Monday, the first trip by a holder of the office since 2005 amid concerns that it could lead to an endorsement rather than scrutiny of China’s rights record. During the six-day trip, Bachelet will visit Xinjiang, where the High Commissioner’s office said last year it believes the mostly Muslim ethnic Uyghurs have been unlawfully detained, mistreated and forced to work. “The purpose of her visit is really focusing on a dialogue with the Chi…