Summary:
```FaultInjectionTestFS``` injects various types of read errors in ```FileSystem``` APIs. One type of error is corruption errors, where data is intentionally corrupted or truncated. There is corresponding validation in db_stress to verify that an injected error results in a user visible Get/MultiGet error. However, for corruption errors, its hard to know when a corruption is supposed to be detected by the user request, due to prefetching and, in case of direct IO, padding. This results in false positives. So remove that functionality.
Block checksum validation for Get/MultiGet is confined to ```BlockFetcher```, so we don't lose a lot by disabling this since its a small surface area to test.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8616
Reviewed By: zhichao-cao
Differential Revision: D30074422
Pulled By: anand1976
fbshipit-source-id: 6a61fac18f95514c15364b75013799ddf83294df
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