Make sure job queue partitions use the null aggregator
- Fixes problem from 37042262e32e
- The main class already handles the calls.
- Partitions call notifyQueueNonEmpty() on pop() even when the other partitions have jobs, so it is also wrong in addition to redundant.
Bug: T101427
Change-Id: Ic3235e1f2038053fabf92f97c663479a21d75317