Temporarily mark QueryPlanKilled as expected on aggregation commands in read_write_concern_defaults_application.js

Context

During aggregation, all involved collections are acquired up front, then released, and re-acquired when pipeline execution starts.
It could happen that the aggregation's target collection appears only after the second acquisition. At that point, the operation would fail with QueryPlanKilled, because a collection participating in the aggregation cannot be created while the aggregation is in progress.