ntpd: let user know if spike was detected

function                                             old     new   delta
update_local_clock                                   861     943     +82

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
ntpd: promote log level 3 to production

Without it, peer selection logic is hard to debug

function                                             old     new   delta
update_local_clock                                   861     982    +121
select_and_cluster                                   962    1065    +103
common_ping_main                                    1788    1821     +33
huft_build                                          1287    1296      +9
chpst_main                                           708     704      -4
INET6_resolve                                        127     119      -8
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 4/2 up/down: 266/-12)           Total: 254 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
ntpd: comment out "spike detection" code

function                                             old     new   delta
update_local_clock                                   982     835    -147

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>