Add wait_for_dns option to default.conf.
    
    This option makes record changes in DNS tree synchronous.
    IPA calls will wait until new data are visible over DNS protocol
    or until timeout.
    
    It is intended only for testing. It should prevent tests from
    failing if there is bigger delay between changes in LDAP and DNS.
    
    Reviewed-By: Petr Viktorin <pviktori@redhat.com>