For many years the message "fsync: giving up on dirty" has occationally
appeared on UFS/FFS filesystems. In some cases it was promptly followed
by a panic of "softdep_deallocate_dependencies: dangling deps". This fix
should eliminate both of these occurences.

Submitted by: Andreas Longwitz <longwitz at incore.de>
Reviewed by: kib
Tested by: Peter Holm (pho)
PR: 225423
MFC after: 1 week