Rename client Minions->Nodes, select the correct path for v1beta3

Replaces the client public interface but leaves old references to "minions"
for a later refactor.  Selects the path "nodes" for v1beta3 and "minions"
for older versions.

pkg/kubectl/describe.go

@@ -176,7 +176,7 @@ type MinionDescriber struct {
 }
 
 func (d *MinionDescriber) Describe(namespace, name string) (string, error) {
-	mc := d.Minions()
+	mc := d.Nodes()
 	minion, err := mc.Get(name)
 	if err != nil {
 		return "", err