Reduced log level of "get hostname error" (#2165)

Reduced log level of "get hostname from http/https request error" to debug so that it won't overwhelms the log file when user is using apache/ngix as their own SSL backend

pkg/util/vhost/vhost.go

@@ -144,7 +144,7 @@ func (v *Muxer) handle(c net.Conn) {
 
 	sConn, reqInfoMap, err := v.vhostFunc(c)
 	if err != nil {
-		log.Warn("get hostname from http/https request error: %v", err)
+		log.Debug("get hostname from http/https request error: %v", err)
 		c.Close()
 		return
 	}