 Eight years ago, prominent 6 billion cybersecurity company FireEye acquired incident response startup Mandiant. That deal has just been undone by a CEO who appears delighted to decouple the two. Kevin Mandia, the chief executive, used the word unlock five times in an investor call Wednesday, where he announced that FireEye has agreed to sell much of its enterprise cybersecurity products business, including the FireEye name, to Symphony Technology Group, a private equity consortium, in an all-cash transaction for 1.2 billion. Shares of FireEye were down almost 6 in trading at market close on Wednesday after the deal was announced. 