Salt master certificates should be stored under `/etc/salt/pki`

[gdemonet]

Component: salt

Why this is needed: To keep things neatly organized

What should be done:

Store all certs used by the salt-master static Pod under /etc/salt/pki:

• SaltAPI server certificate is already at /etc/salt/pki/api/salt-api.crt
• Salt master's kubeconfig is at /etc/salt/master-kubeconfig.conf, should go under /etc/salt/pki/master/kubeconfig.conf
• Salt master's etcd client certificate is at /etc/kubernetes/pki/etcd/salt-master-etcd-client.crt, should go under /etc/salt/pki/master/etcd-client.crt