sync.c: add a module_param to fsync() calls. fsync is still disabled by default but users will have the choice of having a faster build or a safer build (for data integrity). Props for simms for busting my ass off with this one :)
sync: enable the fsync module by default.

Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>
freezer: shorten freezer sleep time using exponential backoff

Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>