This speeds up syncing - now happens only just
two replies from a peer. Especially useful for "ntpd -q".
Shouldn't have ill effects: if we chose a bad peer,
we will discover it later and switch to another one.
The code is even smaller this way.
Suggested by Miroslav Lichvar <mlichvar@redhat.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>