DataIntegrityChecker: File not found is not a fatal error

Modify the logic to gracefully ignore integrity file errors, and allow
the system to create it. Modify the logs to document the errors as wtf
errors, so it would be possible to track with go/apr.

Bug: 130352628
Test: Delete the integrity check file, verify just warning is issued

Change-Id: I37bcac4b12bff4b201904f298d5247855a26e525
1 file changed