clientv3/balancer/grpc1.7-health.go
func (b *GRPC17Health) NeedUpdate() bool {
	// updating notifyCh can trigger new connections,
	// need update addrs if all connections are down
	// or addrs does not include pinAddr.
	b.mu.RLock()
	update := !hasAddr(b.addrs, b.pinAddr)
	b.mu.RUnlock()
	return update
}
func (b *GRPC17Health) NeedUpdate() bool {
	// updating notifyCh can trigger new connections,
	// need update addrs if all connections are down
	// or addrs does not include pinAddr.
	b.mu.RLock()
	update := !hasAddr(b.addrs, b.pinAddr)
	b.mu.RUnlock()
	return update
}
// NeedUpdate returns true if all connections are down or
// addresses do not include current pinned address.