WT-6610It is not an error if the backup rename configuration is not found.
- Retain the value of ret.
- Add test covering upgrade with backup and rename
- Reinstate testing logic lost in merge/reapply
- Fixes if 'rename' is not in the configuration string.
Allow format compatibility to test incremental backup.
Co-authored-by: Alexander Gorrod <firstname.lastname@example.org> | 27 Aug 20 13:42 UTC
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