Use cacheline_aligned in LifoSem
Use cacheline_aligned in LifoSem

Summary: [Folly] Use simpler `cacheline_aligned` v.s. `CachelinePadded` in `LifoSem`, per comments atop `CachelinePadded`.

Reviewed By: aary

Differential Revision: D18166262

fbshipit-source-id: 807c668666fbbc9c16d5f449fa20234e56b29042

facebook/folly,facebook/folly,facebook/folly,facebook/folly,facebook/folly