func (p *nasDatastoreMountProcessor) diffOldNew() []string {
	return p.diff(p.oldHSIDs, p.newHSIDs)
}
func (p *nasDatastoreMountProcessor) diffOldNew() []string {
	return p.diff(p.oldHSIDs, p.newHSIDs)
}
// diffOldNew returns any elements of old that were missing in new.