Issue 51076 - prevent unnecessarily duplication of the target entry
Bug Description: For any update operation the MEP plugin was calling
slapi_search_internal_get_entry() which duplicates
the entry it returns. In this case the entry is just
read from and discarded, but this entry is already
in the pblock (the PRE OP ENTRY).
Fix Description: Just grab the PRE OP ENTRY from the pblock and use
that to read the attribute values from. This saves
two entry duplications for every update operation
from MEP.
fixes: https://pagure.io/389-ds-base/issue/51076
Reviewed by: tbordaz & firstyear(Thanks!!)