dpdk: correct waiting times

When link state interval is 3 and stats interval is 10, updates
for stats will be made every 12 seconds (next number after 10,
that divisible by 3). And if you get counters every 30 secs, you
will get ideal "saw"-line instead of real smooth chart.

This commit makes smooth line on stats intervals that are divisors
of the charts update interval (regardless of link state interval),
and makes it possible to configure them.

Type: fix
Fixes: cb9cadad578297ffd78fa8a33670bdf1ab669e7e
Change-Id: Ia4350467be2b0ec0c1be37c7fda63f43b3330f44
Signed-off-by: Georgy Borodin <bor1-go@yandex-team.ru>