Fix nullifying annotations when there are no labels

[clbx]

Fixes #155

Currently if there are no labels described in the configuration, annotations also get set to an empty map, nuking any annotations set in the configuration.

agent-stack-k8s/internal/scheduler/scheduler.go

Lines 173 to 176 in b5811c8

	if w.k8sPlugin.Metadata.Labels == nil {
	w.k8sPlugin.Metadata.Labels = map[string]string{}
	w.k8sPlugin.Metadata.Annotations = map[string]string{}
	}

This splits them up so that annotations are only set to an empty map if no annotations are described.

[DrJosh9000]

LGTM ✅

Thanks for the contribution!