generic: test i_flags recovery after power failure

generic: test i_flags recovery after power failure

After fsync, filesystem should guarantee inode metadata including
i_flags being persisted, so even after sudden power-cut, during
mount, we should recover i_flags fields correctly, in order to not
loss those meta info.

So adding this testcase to check whether generic filesystem can
guarantee that.

We only check below attribute modification which most filesystem
supports:
- no atime updates (A)
- secure deletion (s)
- synchronous updates (S)
- undeletable (u)

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Reviewed-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>