Ticket 49257 - Reject nsslapd-cachememsize & nsslapd-cachesize when nsslapd-cache-autosize is set
Description: We need to also reject entry cache changes when cache autosizing is being used.
I also found out that we were not registering the ldbm instance callbacks at startup.
So all those functions were only used when creating an instance, and not after it was
Reviewed by: tbordaz(Thanks!)
(cherry picked from commit 35c0834831d5b84ecf723769cea3a806e60525bc)