[modules/dnf] Only do update check every 'interval'
[modules/dnf] Only do update check every 'interval'

Yet another bug in the DNF module - really a troublesome one. Only call
the dnf updateinfo every interval, not every second. That significantly
reduces CPU load.

tobi-wan-kenobi/bumblebee-status,tobi-wan-kenobi/bumblebee-status