v-m: vmstorage: Add pod anti-affinity

One of the reasons for moving to 4 `vmstorage` replicas was to ensure
that the load was spread evenly between the physical VM host machines.
To ensure that is the case as much as possible, we need to keep one
pod per Kubernetes node.

victoria-metrics/vmstorage.yaml

@@ -36,6 +36,18 @@ spec:
         app.kubernetes.io/name: vmstorage
         app.kubernetes.io/component: vmstorage
     spec:
+      affinity:
+        podAntiAffinity:
+          preferredDuringSchedulingIgnoredDuringExecution:
+          - podAffinityTerm:
+              labelSelector:
+                matchExpressions:
+                - key: app.kubernetes.io/name
+                  operator: In
+                  values:
+                  - vmstorage
+              topologyKey: kubernetes.io/hostname
+            weight: 1
       containers:
       - name: vmstorage
         image: docker.io/victoriametrics/vmstorage:v1.96.0-cluster