copy of BZ https://bugzilla.redhat.com/show_bug.cgi?id=2053622

Description of problem:

PodDisruptionBudgetAtLimit Warning alert when CR replica count is zero.

Version-Release number of selected component (if applicable):
4.7

How reproducible: Everytime

Steps to Reproduce:
1. oc new-project test

2. oc new-app httpd

3. oc create -f pdb

$ cat pdb.yaml

~~~
apiVersion: policy/v1beta1
kind: PodDisruptionBudget
metadata:
name: my-pdb
spec:
maxUnavailable: 1
selector:
matchLabels:
deployment: httpd
~~~

$ oc get pdb
NAME MIN AVAILABLE MAX UNAVAILABLE ALLOWED DISRUPTIONS AGE
my-pdb N/A 0 0 3h27m

4. oc scale deployment httpd --replicas=0

5. Wait for some time alert will be triggered at the console.

Actual results: unexpected warning alert

Expected results: As we are intentionally dropping down the replicas it should not generate an alert.