Oil companies in the Middle East are tightening security as U.S. officials say American energy infrastructure in the region is a likely target for Iranian retaliation following the killing by the U.S. of Islamic Revolutionary Guard Corps commander Qassem Soleimani. A call by the U.S. Embassy in Baghdad for all U.S. citizens to leave Iraq is expected to affect staffing at Exxon Mobil Corp., which operates facilities in the country’s volatile southern region. The company should be able to maintain production with local workers,…