Comment 15 for bug 1717040

It's a justification issue, and also trying to keep the general spirit of *Stable* Release Updates (emphasis mine). What problems would we be fixing by updating zesty's zstd from 1.1.2 to 1.3.1, and if they are worth such an update. If it's just multithreading capability, then I think we can skip zesty, given that artful has it and zesty will be end of life in about a month (Jan 2018).