[btrfs-balancer] Run btrfs balancing with Idle IO scheduling class. Contributes to JB#27585
[btrfs-balancer] Run btrfs balancing with Idle IO scheduling class. Contributes to JB#27585

sailfishos/btrfs-balancer,izh1979/btrfs-balancer,sailfishos/btrfs-balancer,izh1979/btrfs-balancer