scheduler should do resource deduction on a cluster as soon as it knows that a new POD will be scheduled onto that cluster

[cathyhongzhang]

What would you like to be added:
The scheduler should update its local cache to deduct the POD resource from the selected cluster/site's total available resource capacity after scheduling decison is made for the POD.

Why is this needed:
There is a time gap between the time that the cluster's resource changes due to POD creation/deletion and the time that the scheduler gets an update about the cluster's total available resource capacity. To reduce chance of scheduling conflict and rescheduling, the scheduler can do resource deduction in time when it knows a new POD will be placed onto a cluster.