fs_stat: ignore timestamp adjustment

- Timestap adjustment happens when a file is created with device time
  set to EPOCH or close time, usually after wiping userdata.
- This is not a file system corruption, so ignore this case when checking
  fs error from fs_stat.

bug: 38513305
Test: unit test, reboots

Change-Id: I23e31e10d8b9f65b61b03854d0b96fefdd013111