AETHER-487 Add support of k8s 1.18

Change-Id: I759b71546e6ba2fc1a52ab135ea26c403fecc417
diff --git a/omec/omec-user-plane/templates/statefulset-upf.yaml b/omec/omec-user-plane/templates/statefulset-upf.yaml
index f17b60d..e570093 100644
--- a/omec/omec-user-plane/templates/statefulset-upf.yaml
+++ b/omec/omec-user-plane/templates/statefulset-upf.yaml
@@ -29,12 +29,20 @@
           {
             "name": "access-net",
             "interface": {{ index $accessConfig "ifname" | quote }},
+{{- if semverCompare ">=1.16-0" .Capabilities.KubeVersion.GitVersion }}
+            "ips": [{{ .Values.config.upf.access.ip | quote }}]
+{{- else }}
             "ips": {{ .Values.config.upf.access.ip | quote }}
+{{- end }}
           },
           {
             "name": "core-net",
             "interface": {{ index $coreConfig "ifname" | quote }},
+{{- if semverCompare ">=1.16-0" .Capabilities.KubeVersion.GitVersion }}
+            "ips": [{{ .Values.config.upf.core.ip | quote }}]
+{{- else }}
             "ips": {{ .Values.config.upf.core.ip | quote }}
+{{- end }}
           }
         ]'
     spec: