Ticket #47780 - Some VLV search request causes memory leaks
    
    Fix description:
    . Modified idl_free interface as follows so that passed idl is cleared
      with NULL once the IDList is successfully freed.
         -idl_free(IDList *idl)
         +idl_free(IDList **idl)
      This change is used to clean up search candidates when ldbm_back_
      search_cleanup (ldbm_search.c) is called as an error return.  The
      cleanup function frees the search candidates when it's not NULL and
      it's not assigned to sr_candidates field in the search result. This
      fixes a memory leak when VLV/Sort op fails.
    . ldbm_back_search_cleanup (ldbm_search.c) calls slapi_send_ldap_result
      if an ldap error is passed to the function.  The logic used to be
      "if (ldap_result>=LDAP_SUCCESS)", which is based upon that mozldap
      return codes are all positive.  Supporting openldap library, there
      is a chance to get a negative return code (e.g. LDAP_PARAM_ERROR ==
      -9).  This patch supports the negative return codes, as well.
    . In ldbm_back_search (ldbm_search.c) vlv_filter_candidates could
      ruturn errors such as and LDAP_TIMELIMIT_EXCEEDED, LDAP_ADMINLIMIT_
      EXCEEDED.  The search results are supposed to be returned to the
      client with the error code if the control is not critical.  The code
      is added.
    . The VLV operation stores the result in vlv_response_control.result
      in ldbm_back_search (ldbm_search.c), which occurs at 3 places, vlv_
      filter_candidates, sort_candidates and vlv_trim_candidates_txn.
      The return code from the latter calls used to override the former
      return code.  This patch fixes it to respect the former return code.
    
    https://fedorahosted.org/389/ticket/47780
    
    Reviewed by rmeggins@redhat.com (Thank you, Rich!!)
    
    (cherry picked from commit 1118cc9b61a60c704250080d6af8785e4f8d28af)
    (cherry picked from commit e9f86dab95fd600b414cf1c4cf6f7c733348b758)
    (cherry picked from commit ff4c7a7b3f65589f93d88aadfcbe95976a9b31a9)