Microfixes to autoscale.go (#7594)
Microfixes to autoscale.go (#7594)

* Microfixes to autoscale.go

- Stop permitting 0 mb/prime since this is errorneous input.
- Stop checking 0 for delays, since it's not error, in general, but just
  useless.

* err
knative/serving,knative/serving