Use python3 for the mininet entry point

Change-Id: Idfaff80c3638c8aad7a8affa40ae480aaf9d40ca
diff --git a/mininet/templates/deployment.yaml b/mininet/templates/deployment.yaml
index 25a0031..9ad2e5b 100644
--- a/mininet/templates/deployment.yaml
+++ b/mininet/templates/deployment.yaml
@@ -41,7 +41,7 @@
           image: "{{ .Values.global.registry }}{{ .Values.images.mininet.repository }}:{{ tpl .Values.images.mininet.tag . }}"
           imagePullPolicy: {{ .Values.images.mininet.pullPolicy }}
 {{- if gt ($.Values.mnStratumSwitchCount|int) 0 }}
-          command: ["python"]
+          command: ["python3"]
 {{- end }}
           args: [{{ .Values.topoScript }}]
           stdin: true