In order to support claiming reservation atomically (
IMPALA-3748) and distributing it to different execution nodes, we need to add a transfer operation to ReservationTrackers.
The idea is that we would claim all the reservation in a single shared "initial reservation" tracker, then individual nodes could claim their share from there. When a node is closed, and other node that executes after it depends on getting its reservation, it would have to deposit its initial reservation back into the "initial reservation" tracker (or transfer it directly to the other node).
This operation should