Add index on idnsName
    
    The data structures for the internal DNS server use the attribute idnsName
    instead of cn in the DN. It's also used to search for entries when entries
    are added, modified, or removed.
    
    The new index speeds up dnsrecord and dnszone related commands as well
    as commands like host-add and host-del --updatedns.
    
    Fixes: https://pagure.io/freeipa/issue/7803
    Signed-off-by: Christian Heimes <cheimes@redhat.com>
    Reviewed-By: Florence Blanc-Renaud <frenaud@redhat.com>