Overwrite the default affinity

[clyang82]

The previous PR #23 is for defining some common affinity. for example:

    affinity:
      nodeAffinity:
        requiredDuringSchedulingIgnoredDuringExecution:
          nodeSelectorTerms:
          - matchExpressions:
            - key: kubernetes.io/e2e-az-name
              operator: In
              values:
              - e2e-az1
              - e2e-az2

This PR is for defining the default affinity just like what we do in receiver component:

podAntiAffinity:
      preferredDuringSchedulingIgnoredDuringExecution:
      - podAffinityTerm:
          labelSelector:
            matchExpressions:
            - key: app.kubernetes.io/name
              operator: In
              values:
              - thanos-query
            - key: app.kubernetes.io/instance
              operator: In
              values:
              - observatorium-xyz
          topologyKey: kubernetes.io/hostname
        weight: 30
      - podAffinityTerm:
          labelSelector:
            matchExpressions:
            - key: app.kubernetes.io/name
              operator: In
              values:
              - thanos-query
            - key: app.kubernetes.io/instance
              operator: In
              values:
              - observatorium-xyz
          topologyKey: topology.kubernetes.io/zone
        weight: 70

/assign @metalmatze

Signed-off-by: clyang82 chuyang@redhat.com

[clyang82]

Thanks @metalmatze . Could you help to merge it? I do not have permission to do it.