remove min_interval_seconds from plugin workers and default vacuum interval to 17m
The worker-level min_interval_seconds was redundant with the admin-side
DetectionIntervalSeconds, complicating scheduling logic. Remove it from
vacuum, volume_balance, erasure_coding, and ec_balance handlers.
Also change the vacuum default DetectionIntervalSeconds from 2 hours to
17 minutes to match the previous default behavior.
2604ec7deb