Enable Affinitiy and Anti-Affinity

Affinitiy and Anti-Affinity is supported by all TestNF release bits.

Follow the below steps to enable it.

• Prepare values.yml to have contents like this. The content follow the same format as https://kubernetes.io/docs/concepts/scheduling-eviction/assign-pod-node/#affinity-and-anti-affinity.

affinity:                           
  nodeAffinity:           
    requiredDuringSchedulingIgnoredDuringExecution:           
      nodeSelectorTerms:               
      - matchExpressions:               
        - key: disktype                 
          operator: In                 
          values:                 
          - ssd             

• Follow Instantiation Page to instantiate testnf-du-large and select the prepared values.yml.