Modify nodes to register directly with the master.

- Delete nodes when they are no longer ready and don't exist in the
cloud provider.
 - Label each node with it's hostname.
 - Add flag to skip node registration.
 - Add a test for registering an existing node.

pkg/api/validation/validation.go

@@ -1195,6 +1195,8 @@ func ValidateNodeUpdate(oldNode *api.Node, node *api.Node) errs.ValidationErrorL
 	oldNode.ObjectMeta = node.ObjectMeta
 	// Allow users to update capacity
 	oldNode.Status.Capacity = node.Status.Capacity
+	// Allow the controller manager to assign a CIDR to a node.
+	oldNode.Spec.PodCIDR = node.Spec.PodCIDR
 	// Allow users to unschedule node
 	oldNode.Spec.Unschedulable = node.Spec.Unschedulable
 	// Clear status