Ticket 50236 - memberOf should be more robust
Bug Description: When doing a modrdn, or any memberOf update, if the entry
already has the memberOf attribute with the same value
the operation is incorrectly rejected.
Fix Description: If we get an error 20 (type or value exists) return success.
Also fixed a coding mistake that causes the wrong error
code to be returned. This also required fixing the CI
test to check for the new correct errro code.
https://pagure.io/389-ds-base/issue/50236
Reviewed by: firstyear, spichugi, and tbordaz (Thanks!!!)