This is causing problems with the Kubernetes 1.19 code-generator.
A nil entry in these slices wouldn't be valid anyways, so this should have no impact.
- switching to using code rather than a template for the systemd unit creation as requested in review
- as part of the review, changing the name of the ca from tls-ca to tls-client-ca
- changing the api from DisableAddressCheck to EnableAddressCheck and defaulting to true if no set
- fixing up the test for node-authorizer and shifting the parsing of the certificates as suggested in reviews to a method