[4.9]  "MachineNotYetDeleted" in Pending state alert not fired

Version - Cluster version is 4.9.0-0.nightly-2021-06-25-050351
Requirement - https://issues.redhat.com/browse/OCPCLOUD-921

Steps :
1. Create a PDB refer below 

apiVersion: policy/v1
kind: PodDisruptionBudget
metadata:
  name: pdb1
spec:
  minAvailable: 7
  selector:
    matchLabels:
      app: nginx

Pdb created successfully 
2.create deployment which have same replicas as minAvailable in the PDB refer below :

apiVersion: apps/v1
kind: Deployment
metadata:
  name: "dep1"
spec:
  replicas: 7
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
     containers:
     -
       name: "myfrontend"
       image: "quay.io/openshifttest/hello-openshift@sha256:aaea76ff622d2f8bcb32e538e7b3cd0ef6d291953f3e7c9f556c1ba5baf47e2e"
       ports:
        -
          containerPort: 80
          name: "http-server"
Deployment created successfully 
3.Delete worker machine running pods
Expected - machine stuck in deleting phase , after 6 hrs Alert “MachineNotYetDeleted” is fired
Actual - machine stuck in deleting phase but after 6 hrs Alert “MachineNotYetDeleted” is in pending state