Use python3 for the mininet entry point

Change-Id: Idfaff80c3638c8aad7a8affa40ae480aaf9d40ca
diff --git a/mininet/Chart.yaml b/mininet/Chart.yaml
index 0526f6b..0a5f10e 100644
--- a/mininet/Chart.yaml
+++ b/mininet/Chart.yaml
@@ -18,4 +18,4 @@
 appVersion: 1.1.0
 description: A Helm chart for Mininet
 name: mininet
-version: 1.2.0
+version: 1.2.1