The metadata and turtle files are very important. We should add in testing to make sure a failure between writing out the temporary turtle file and renaming it into place does the right thing.

The function wt_turtle_update creates the WT_METADATA_TURTLE_SET file. Once complete, it calls wt_sync_and_rename.

We should consider adding failure testing between the sync and rename (which forces a panic) and verify the correct behavior exists on restart. wt_sync_and_rename is used for any atomic file placement.