Ticket 50238 - Failed modrdn can corrupt entry cache
Bug Description: Under certain conditions (found under IPA) when a backend
transaction plugin fails and causes a modrdn operation to
fail the entry cache no longer contains the original/pre
entry, but instead it has the post modrdn'ed entry with
the original entry's ID
Fix Description: Upon failure, if the post entry is in the cache, then swap
it out with the original entry.
https://pagure.io/389-ds-base/issue/50238
Reviewed by: firstyear, spichugi, & tboardaz (Thanks!!!)