vsphere/tags_helper.go
func (p *tagDiffProcessor) diffNewOld() []string {
	return p.diff(p.newTagIDs, p.oldTagIDs)
}
func (p *tagDiffProcessor) diffNewOld() []string {
	return p.diff(p.newTagIDs, p.oldTagIDs)
}
// diffNewOld returns any elements of new that were missing in old.