By Andrew MacAskill LONDON (Reuters) – British Prime Minister Rishi Sunak suffered a setback to his plans to deport some asylum seekers to Rwanda after parliament’s upper house backed a largely symbolic motion to delay ratification of a treaty aimed at overcoming a legal block. Under the Rwanda plan, which has yet to be carried out, asylum seekers who arrive on England’s southern coast in small, inflatable boats would be sent to Rwanda. In an effort to overcome resistance from the courts who have ruled the plan is unlawful, Britain signed a treaty last year with Rwanda, in which it agreed to a…