Revert "sched: Set MC (multi-core) sched domain's busy_factor attribute to 1"

This reverts commit c736af3978c9eca0bdf73bfdf1370e388c5c2dff.
Revert "fs/sync: Make sync() satisfy many requests with one invocation"

This reverts commit 122321cc34f61238a45c9f722b5bc03d58de5281.