Tests: fix TestShutdownTCP race using NotifyStartedFunc
Tests: fix TestShutdownTCP race using NotifyStartedFunc

asergeyev/dns,hugozhu/dns,ezoic/dns,tempbottle/dns,janstk/dns,michaelharo/dns,bboreham/dns,tsenart/dns,jdef/dns,curtiszimmerman/dns,skynet/dns,ym/go-dns,josephyzhou/dns,ErikDubbelboer/dns,jmhodges/dns,benbearchen/dns,modulexcite/dns,flebarbe/dns,Psiphon-Inc/dns,cloudflare/dns,miekg/dns,bragr/dns,Git-Host/dns,rolandshoemaker/dns,letsencrypt/dns,skyportsystems/dns