fix(orchestra): missing node_selector in helm test template

[fbuchmeier-abi]

This fixes: #163

Successful helm template & kubectl validate:

kubectl validate <(helm template test ./orchestra --set services.node_selectors.'kubernetes\.io/arch'=amd64 --show-only templates/tests/precheck.yaml )
coalesce.go:289: warning: destination for orchestra.services.node_selectors is a table. Ignoring non-table value ([])

/proc/self/fd/11...OK

Helm template output:

---
# Source: orchestra/templates/tests/precheck.yaml
apiVersion: v1
kind: Pod
metadata:
  name: test-orchestra-test
  namespace: default
  annotations:
    "helm.sh/hook": pre-install,pre-upgrade
    "helm.sh/hook-weight": "-5"
    "helm.sh/hook-delete-policy": hook-succeeded,before-hook-creation
    sidecar.istio.io/inject: "false"
    argocd.argoproj.io/sync-wave: "20"
spec:
  restartPolicy: Never
  containers:
    - name: test-values
      image: ghcr.io/tremolosecurity/python3:1.0.0
      imagePullPolicy: Always
      command: ["python", "/scripts/check-hosts.py"]
      securityContext:
        allowPrivilegeEscalation: false
        capabilities:
          drop:
          - "ALL"
        
        seccompProfile:
          type: RuntimeDefault
        runAsNonRoot: true
        runAsUser: 431
        runAsGroup: 433
        
      volumeMounts:
      - name: scripts
        mountPath: "/scripts"
        readOnly: true
      - name: tmp-pad
        mountPath: "/tmp-pad"
  
  securityContext:
    fsGroup: 433
    supplementalGroups: [433]
    seccompProfile:
      type: RuntimeDefault
    runAsNonRoot: true
    runAsUser: 431
    runAsGroup: 433
  
  
  
  nodeSelector: 
    kubernetes.io/arch: "amd64"
  
  
  
  volumes:
    - name: scripts
      configMap:
        name: check-hosts-test
    - name: tmp-pad
      emptyDir: {}

[fbuchmeier-abi]

I just saw that my changes from #153 are also in this PR. @mlbiam if you could look at this first and 164 later this would save me some trouble in regards to our Open Source Contribution process :)