antiaffinity selector never matches (#7700)

Tested in minikube by replacing the zookeeper image with the pause container and the scheduler was able to schedule all 3 pods on the minikube node. Changing it to zk, made the pods zk-1 and zk-2 pending with scheduling failure as expected.

docs/tutorials/stateful-application/zookeeper.yaml

@@ -63,7 +63,7 @@ spec:
                   - key: "app"
                     operator: In
                     values:
-                    - zk-hs
+                    - zk
               topologyKey: "kubernetes.io/hostname"
       containers:
       - name: kubernetes-zookeeper