LDAP Content Sync in general and "syncrepl" should only be used
when referring to replication-specific functionality.

to already-freed memory. That bug still needs to be tracked down. This
patch deletes curcsn and just uses op->o_csn, which did not exist when
this code was originally written.

  syncrepl: don't save contextCSN on incoming context entry
  syncprov: delete contextCSN on checkpoint if ctxcsn is empty

cookie, that's only an intermediate value.
ITS#4622, don't update the context cookie until all the nonpresent
deletes are finished.

cleanup overlay list if overlay db_init fails.

busy unnecessarily

looking for, don't cache anything else.