Additional certificate domain

[vrumjantsev]

It would be useful to add private svc domain to pregenerated certificates for easier usage inside the k8s.
Otherwise certificate cannot be validated while using private address

(x509: certificate is valid for localhost, cockroachdb-test-public, cockroachdb-test-public.playground, cockroachdb-test-public.playground.svc.cluster.local, *.cockroachdb-test, *.cockroachdb-test.playground, *.cockroachdb-test.playground.svc.cluster.local, not cockroachdb-test.playground.svc.cluster.local)