MEXICO CITY (Reuters) - U.S. Attorney General William Barr spoke with Mexican Foreign Minister Marcelo Ebrard last week to try to lower bilateral tension arising from the U.S. arrest of a former Mexican defense minister on drugs charges, two Mexican sources said on Monday. Mexico says it should have had prior warning about the arrest and investigation of the former minister and retired army officer, Salvador Cienfuegos, who pleaded not guilty to drug charges in a Brooklyn federal court last week. Mexico's President Andres Manuel Lopez Obrador has said he will announce a review of security cooperation agreements with the...