return after Skip is unreachable
Remove bucket rescan rest stuff
Load databases on demand

Databases are no longer preloaded and are now fully evicted from memory
when passivated.
Remove unused method
Send quiesce through the normal close API
Run periodic tasks without relinquishing control

This change prevents a deadlock in the registration/quiescence
interaction while keeping the same semantics regarding concurrent job
execution.

I also reworked the test slightly to use atomics since the race detector
pointed out that was a good idea.
Move low-level bucket listing into test (where it's used)