When a lifecycle hook is called, but has nothing to do, return a "successful" response

[dlipovetsky]

Currently, a lifecycle hook does not set a response status when it has nothing to do, e.g., when its specific variable is not found. Example:

cluster-api-runtime-extensions-nutanix/pkg/handlers/generic/lifecycle/cni/calico/handler.go

Lines 117 to 123 in fde18b8

	if variables.IsNotFoundError(err) {
	log.V(5).
	Info(
	"Skipping Calico CNI handler, cluster does not specify request CNI addon deployment",
	)
	return
	}

.

(Otherwise, a lifecycle hook sets the response status to either success or failure.)

The topology controller that calls the lifecycle hook interprets a lack of status as success, but if we explicitly set the status, we can have a better record of what the hooks are doing.

Let's define an internal error type that the handler can return when it has nothing to do, and a higher-level wrapper can return a "successful" response with a predictable message, something along the lines of handler NAME skipped, because it has no input