Remove dnspatch we have not used it anymore (#2198)

assets/go-dnsclient.patch

@@ -1,18 +0,0 @@
-296a297,300
-> 	conf.update(name)
-> }
-> 
-> func (conf *resolverConfig) update(name string) {
-300a305,316
-> }
-> 
-> func UpdateDnsConf() {
-> 	resolvConf.initOnce.Do(resolvConf.init)
-> 
-> 	// Ensure only one update at a time checks resolv.conf.
-> 	if !resolvConf.tryAcquireSema() {
-> 		return
-> 	}
-> 	defer resolvConf.releaseSema()
-> 
-> 	resolvConf.update("/etc/resolv.conf")