Ticket 49298 - force sync() on shutdown
Bug Description: During shutdown on xfs we would occasionally
see a broke dse.ldif (specifically, empty). This happens due to
a bug in xfs where the directory isn't synced on rename().
Fix Description: As we shutdown call sync() to force all our
writes to disk - dse.ldif, logs, db, all of it.
https://pagure.io/389-ds-base/issue/49298
Author: wibrown
Review by: mreynolds (Thanks!)