SEOUL (Reuters) – North Korea’s foreign minister returned from Russia on Friday after a rare official visit and meeting with President Vladimir Putin as part of closer cooperation that Washington said could drastically change the security threat posed by Pyongyang. Foreign Minister Choe Son Hui and a government delegation returned home on Friday, official news agency KCNA said without elaborating on her meetings in Moscow. Earlier this week, KCNA said Choe and Russian Foreign Minister Sergei Lavrov discussed strengthening the “strategic and tactical cooperation” and implementing the agreement …