Enable hairpinMode in flannel CNI config

* Allow pods to communicate with themselves via service IP
* flannel-io/flannel#849

Author: dghubble

pkg/asset/internal/templates.go

@@ -1106,6 +1106,7 @@ data:
         {
           "type": "flannel",
           "delegate": {
+            "hairpinMode": true,
             "isDefaultGateway": true
           }
         },