--dns-domain argument not applied to kubernetes API server certificate generation

[shaneramey]

Is this a BUG REPORT or FEATURE REQUEST? (choose one):

BUG REPORT

Minikube version (use minikube version):
v0.19.0

Environment:

• OS: MacOS
• VM Driver: virtualbox
• ISO version: v0.18.0
• Install tools:
• Others:

What happened:
I set up a new minikube cluster with the following command:
minikube start --dns-domain=test.local

The cert assigned to the Kubernetes API is still signed for "kubernetes.default.svc.cluster.local", despite passing the --dns-domain argument

What you expected to happen:

The API TLS cert should be signed for kubernetes.default.svc.test.local

How to reproduce it (as minimally and precisely as possible):

minikube start --dns-domain=test.local
openssl s_client -showcerts -connect `minikube ip`:8443

The cert from the above output shows that it is signed for kubernetes.default.svc.cluster.local

Anything else do we need to know:
Without the kubernetes API signed with the cluster domain, in-cluster TLS validation fails when attempting to hit https://kubernetes.default.svc.test.local