f2fs: enforce fsync_mode=strict for renamed directory

This is to give a option for user to be able to recover B/foo in the below
case.

mkdir A
sync()
rename(A, B)
creat (B/foo)
fsync (B/foo)
---crash---

Sugessted-by: Velayudhan Pillai <vijay@cs.utexas.edu>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>