The biggest state-controlled refiners in China are considering whether to buy Iranian crude after the U.S. on Friday issued a one-month waiver allowing imports of Iran-origin crude, sources with knowledge of the situation told Bloomberg on Monday. China has been the biggest and nearly the only buyer of Iranian crude in recent years amid the U.S. sanctions on Iran’s exports, but all these sanctioned barrels were flowing on dark fleets to the independent Chinese refiners. These crude processors, commonly referred to as teapots, don’t…