c8d: Add the events services to the containerd image service
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**- What I did**

Added the `EventsService` to the containerd image service and implemented `LogImageEvent`.
I removed the `LogImageEventWithAttributes` since it wasn't used anywhere.

No events are sent yet, these will come at a later stage.

**- How I did it**

**- How to verify it**

**- Description for the changelog**
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daemon/containerd/image_events.go
package containerd

// LogImageEvent generates an event related to an image with only the
// default attributes.
func (i *ImageService) LogImageEvent(imageID, refName, action string) {
	panic("not implemented")
}

// LogImageEventWithAttributes generates an event related to an image with
// specific given attributes.
func (i *ImageService) LogImageEventWithAttributes(imageID, refName, action string, attributes map[string]string) {
	panic("not implemented")
}

package containerd

import (
	"context"

	"github.com/docker/docker/api/types/events"
	imagetypes "github.com/docker/docker/api/types/image"
)

// LogImageEvent generates an event related to an image with only the default attributes.
func (i *ImageService) LogImageEvent(imageID, refName, action string) {
	ctx := context.TODO()
	attributes := map[string]string{}

	img, err := i.GetImage(ctx, imageID, imagetypes.GetImageOpts{})
	if err == nil && img.Config != nil {
		// image has not been removed yet.
		// it could be missing if the event is `delete`.
		copyAttributes(attributes, img.Config.Labels)
	}
	if refName != "" {
		attributes["name"] = refName
	}
	actor := events.Actor{
		ID:         imageID,
		Attributes: attributes,
	}

	i.eventsService.Log(action, events.ImageEventType, actor)
}

// copyAttributes guarantees that labels are not mutated by event triggers.
func copyAttributes(attributes, labels map[string]string) {
	if labels == nil {
		return
	}
	for k, v := range labels {
		attributes[k] = v
	}
}

```suggestion
```
That's redundant. A `nil` map is equivalent to an empty map for purposes of `range`.