Ensure logio data is persisted on user fsync()

[MichaelBrim]

Description

This PR makes it so we persist logio data to storage when a client uses fsync(), unless the client.fsync_persist configuration option is used to disable this behavior.

Motivation and Context

See issue #645

How Has This Been Tested?

Tested in Ubuntu Docker container

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Performance enhancement (non-breaking change which improves efficiency)
• Code cleanup (non-breaking change which makes code smaller or more readable)
• Breaking change (fix or feature that would cause existing functionality to change)
• Testing (addition of new tests or update to current tests)
• Documentation (a change to man pages or other documentation)

Checklist:

• My code follows the UnifyFS code style requirements.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.
• All commit messages are properly formatted.

[adammoody]

Great! Thanks, @MichaelBrim !

Since this is moved up into the wrapper, I think we'll want to capture any other calls that do something similar. I think fdatasync and sync would be on that list, assuming we have wrappers for them.

I also checked fflush, but its man page says that it doesn't sync data to disk. Instead, one must call fflush and then follow that with something like fsync.