For dev, don't preload docker images on nodes

[justinsb]

If we're not going to use the docker images, we don't need to preload
them - saves a bit off the boot time.

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[hakman]

Nice! This saves me a PR.

In the same context, shouldn't the LoadImage task be in the ProtokubeBuilder?

kops/upup/pkg/fi/nodeup/command.go

Lines 304 to 310 in 0b52b99

	if c.config.ProtokubeImage != nil {
	taskMap["LoadImage.protokube"] = &nodetasks.LoadImageTask{
	Sources: c.config.ProtokubeImage.Sources,
	Hash: c.config.ProtokubeImage.Hash,
	Runtime: c.cluster.Spec.ContainerRuntime,
	}
	}

[rifelpet]

shoot, should have merged this before #8258

[rifelpet]

/test pull-kops-e2e-kubernetes-aws

[justinsb]

Also moved the protokube image loading into ProtokubeBuilder - thanks for the suggestion @hakman!

[rifelpet]

/lgtm