Failing pod never times out

## In what area(s)?
/area autoscale

## What version of Knative?

HEAD

## Expected Behavior

When a pod fails to start properly it should eventually be terminated.

## Actual Behavior

If an instance/pod fails to start and it is the first time the revision is starting a pod then the pod will eventually be terminated. But, if the first instance of the revision starts ok, then scales down to zero, if the next instance/pod that is created fails to start then the pod will continually crash-loop (which is expected) but it'll never be terminated and never goes away.

It seems like there should be consistency between a "first time pod" and a "2+ time pod" w.r.t. what happens when it crashes.

## Steps to Reproduce the Problem

You can reproduce this by running this bash script:
```
#!/bin/bash

set -e
kubectl delete ksvc/bugsvc > /dev/null 2>&1 || true
kubectl delete ksvc/bugsvc2 > /dev/null 2>&1 || true

export CRASH=$(( $(date -u '+%s') + 120))

echo "Time now: ${now:15:5}
echo "Will die: ${CRASH}

kubectl apply -f - <