Adding support for TLS MinVersion and CipherSuites

This will watch for the following kube-apiserver-arg variables and apply
them to the k3s kube-apiserver https listener.

  --kube-apiserver-arg=tls-cipher-suites=XXXXXXX
  --kube-apiserver-arg=tls-min-version=XXXXXXX

pkg/cluster/https.go

@@ -33,7 +33,9 @@ func (c *Cluster) newListener(ctx context.Context) (net.Listener, http.Handler,
 		CN:           "k3s",
 		Organization: []string{"k3s"},
 		TLSConfig: tls.Config{
-			ClientAuth: tls.RequestClientCert,
+			ClientAuth:   tls.RequestClientCert,
+			MinVersion:   c.config.TLSMinVersion,
+			CipherSuites: c.config.TLSCipherSuites,
 		},
 		SANs: append(c.config.SANs, "localhost", "kubernetes", "kubernetes.default", "kubernetes.default.svc."+c.config.ClusterDomain),
 	})