imagebuilder: ignore terminated builder instance
imagebuilder: ignore terminated builder instance

We reuse the instance if it already exists, but we weren't ignoring
terminated instances.

luxas/kube-deploy,krousey/kube-deploy,luxas/kube-deploy,ostrichops/kube-deploy,ajitak/kube-deploy,ostrichops/kube-deploy,krousey/kube-deploy,ostrichops/kube-deploy,justinsb/kube-deploy,justinsb/kube-deploy,justinsb/kube-deploy,ajitak/kube-deploy,luxas/kube-deploy