Not working on k8s v1.21.0

[bhsrinivasan-px]

I think the stateful set needs to be updated, in order to run on k8s versions 1.21.0 and above

apiVersion: "apps/v1"
kind: StatefulSet
metadata:
  name: cassandra
spec:
  serviceName: cassandra
  replicas: 3
  selector:
    matchLabels:
      app: cassandra
  template:
    metadata:
      labels:
        app: cassandra
...
...