[stable/mongodb] Support affinity in template (#7455)

It currently exists in `values.yaml' but never used

Signed-off-by: Yujun Zhang <yujunz@nvidia.com>

stable/mongodb/Chart.yaml

@@ -1,5 +1,5 @@
 name: mongodb
-version: 4.2.1
+version: 4.2.2
 appVersion: 4.0.2
 description: NoSQL document-oriented database that stores JSON-like documents with dynamic schemas, simplifying the integration of data in content-driven applications.
 keywords:

stable/mongodb/templates/deployment-standalone.yaml

@@ -21,6 +21,10 @@ spec:
         fsGroup: {{ .Values.securityContext.fsGroup }}
         runAsUser: {{ .Values.securityContext.runAsUser }}
       {{- end }}
+      {{- if .Values.affinity }}
+      affinity:
+{{ toYaml .Values.affinity | indent 8 }}
+      {{- end -}}
       {{- if .Values.nodeSelector }}
       nodeSelector:
 {{ toYaml .Values.nodeSelector | indent 8 }}