Don't set ingress for services which have not auth module. You can add ingress by using the following template. After add ingress, all traffic will be forward to kong firstly.
echo "apiVersion: extensions/v1beta1
kind: Ingress
metadata:
name: demo
annotations:
plugins.konghq.com: ldap-auth
spec:
rules:
- http:
paths:
- path: /foo
backend:
serviceName: httpbin
servicePort: 80" | kubectl apply -f -
helm install --name fission -f configs/fission/config.yaml charts/fission-all
More Details at https://github.com/fission/fission/tree/master/charts