Peroidic STP timers don't have to be exact.  The hold timer runs at
1HZ, and the hello timer normally runs at 2HZ; save power by aligning
it them to next second.
Signed-off-by: NStephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>