f2fs/022: do sanity check on footer of non inode dnode

This is a regression test:
1. create foo & bar
2. write 8M data to foo
3. use inject.f2fs to inject i_nid[0] of foo w/ ino of bar
4. fpunch in foo w/ specified range

If we haven't applied kernel patch ("f2fs: fix to do sanity check on
node footer for non inode dnode"), f2fs may missed to do sanity check
on corrupted dnode, result in panic or deadloop in step 4).

Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Chao Yu <chao@kernel.org>
Reviewed-by: Zorro Lang <zlang@redhat.com>
Signed-off-by: Zorro Lang <zlang@kernel.org>