After the move of the zone dumping process, we can slightly reduce the scheduling priority of the zone dumping process. This is either done by setting the SCHED_BATCH priority at the beginning and SCHED_OTHER (aka SCHED_NORMAL) back when the zone dumping is done.
(On Windows, this is done by using THREAD_MODE_BACKGROUND_BEGIN and THREAD_MODE_BACKGROUND_END combo.)
Closes #2732 (closed)