Gangway gives an empty CA when outputting kubeconfig

[iaguis]

When deploying Dex+Gangway to a new cluster and trying to log in, the CLI instructions show this:

echo "" \ > /tmp/ca-test-oidc.pem

In quotes should be the cluster CA but it is empty.

This happens because Gangway is using the default service account and since #704 we don't mount it in pods by default. This causes the CA file that Gangway expects (/var/run/secrets/kubernetes.io/serviceaccount/ca.crt) not to be in the pod file system.