[Helm] certificate lifecycle management

[petermikitsh]

Currently, the helm <-> tiller connection is secured via TLS/SSL. We generate a Certificate Authority that's good for 20 years, a Helm certificate that's valid for 1 year, and a Tiller certificate that's also valid for 1 year.

Inevitably, the CA and Certificates are going to expire, and will need to be re-created, and their lifecycle managed accordingly. Practically speaking, since helm is only used during cluster creation, their expiration won't break deployments -- so this won't impact end users.