Ticket 48132 - modrdn crashes server (invalid read/writes)
Bug Description: When performing a modrdn stress test using two masters
a double free can occur that will lead to a crash. When
the server is under load it might have to retry the modrdn
operation. During this retry the SLAPI_MODRDN_EXISTING_ENTRY
entry was previosuly replaced, and it can be freed twice on
the second retry..
Fix Description: Check if entry being retuned form the cache is the same as
the entry stored in SLAPI_MODRDN_EXISTING_ENTRY, if it is,
set it to NULL so it is not freed again.
https://fedorahosted.org/389/ticket/48132
valgrind: PASSED
Reviewed by: nhosoi(Thanks!)
(cherry picked from commit 1d9ae0f4a1ea12463ac59a04da5e6572db002d73)