Exposing CA keys in a mine creates a security flaw, thus such
should be avoided.
This change removes code responsible for putting and retrieving
CA key from a mine and changes the ca.sls state to allow configuring
where CA cert and its key would be generated as well as their owners.

Fixes PROD-13439

Change-Id: I6d78b13dcb3754c51606edd7e2d8158e128244a4