By Ahmed Aboulenein and Susan Heavey WASHINGTON (Reuters) -Abbott Laboratories and the U.S. Food and Drug Administration are on track to reopen Abbott’s baby formula manufacturing plant in Sturgis, Michigan, within one or two weeks, FDA Commissioner Robert Califf said on Thursday. Abbott, the biggest U.S. supplier of powder infant formula, including Similac, on Monday agreed with the FDA on steps needed to resume production at the plant. “I’m pleased to say today we’ve already made significant progress and I think we are on track to get it open within the next week to two weeks, most likely at…