UPSTREAM: f2fs: clean up zones when not successfully unmounted

We can't trust write pointers when the previous mount was not
successfully unmounted.

Change-Id: If67696db9ab820a805711b43cabb50c796c9f75f
Signed-off-by: Daeho Jeong <daehojeong@google.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
(cherry picked from commit 9f792ab8)