agent/engine/docker_image_manager.go
func (imageManager *dockerImageManager) removeImageState(imageStateToBeRemoved *image.ImageState) {
	for i, imageState := range imageManager.imageStates {
		if imageState.Image.ImageID == imageStateToBeRemoved.Image.ImageID {
			// Image State found; hence remove it
			seelog.Infof("Removing Image State: [%s] from Image Manager", imageState.String())
			imageManager.imageStates = append(imageManager.imageStates[:i], imageManager.imageStates[i+1:]...)
			return
		}
	}
}
func (imageManager *dockerImageManager) removeImageState(imageStateToBeRemoved *image.ImageState) {
	for i, imageState := range imageManager.imageStates {
		if imageState.Image.ImageID == imageStateToBeRemoved.Image.ImageID {
			// Image State found; hence remove it
			seelog.Infof("Removing Image State: [%s] from Image Manager", imageState.String())
			imageManager.imageStates = append(imageManager.imageStates[:i], imageManager.imageStates[i+1:]...)
			return
		}
	}
}
// removeImageState removes the imageState from the list of imageState objects in ImageManager