* whois: use the upstream server to resolve whois server hostname

Close AdguardTeam#1535

Squashed commit of the following:

commit 7755d7a
Merge: e24e945 5c2ca69
Author: Simon Zolin <s.zolin@adguard.com>
Date:   Wed May 27 14:41:24 2020 +0300

    Merge remote-tracking branch 'origin/master' into 1535-whois-resolve

commit e24e945
Merge: db76471 355e634
Author: Simon Zolin <s.zolin@adguard.com>
Date:   Wed May 27 14:29:44 2020 +0300

    Merge remote-tracking branch 'origin/master' into 1535-whois-resolve

commit db76471
Author: Simon Zolin <s.zolin@adguard.com>
Date:   Wed May 27 12:57:00 2020 +0300

    fix

commit dc38f66
Author: Simon Zolin <s.zolin@adguard.com>
Date:   Wed May 27 12:44:10 2020 +0300

    * whois: use the upstream server to resolve whois server hostname

home/whois.go

@@ -1,6 +1,7 @@
 package home
 
 import (
+	"context"
 	"encoding/binary"
 	"fmt"
 	"io/ioutil"
@@ -120,7 +121,7 @@ func (w *Whois) query(target string, serverAddr string) (string, error) {
 	if addr == "whois.arin.net" {
 		target = "n + " + target
 	}
-	conn, err := net.DialTimeout("tcp", serverAddr, time.Duration(w.timeoutMsec)*time.Millisecond)
+	conn, err := customDialContext(context.TODO(), "tcp", serverAddr)
 	if err != nil {
 		return "", err
 	}

home/whois_test.go

@@ -2,11 +2,29 @@ package home
 
 import (
 	"testing"
+	"time"
 
+	"github.com/AdguardTeam/AdGuardHome/dnsforward"
+	"github.com/AdguardTeam/dnsproxy/proxy"
 	"github.com/stretchr/testify/assert"
 )
 
+func prepareTestDNSServer() error {
+	config.DNS.Port = 1234
+	Context.dnsServer = dnsforward.NewServer(nil, nil, nil)
+	conf := &dnsforward.ServerConfig{}
+	uc, err := proxy.ParseUpstreamsConfig([]string{"1.1.1.1"}, nil, time.Second*5)
+	if err != nil {
+		return err
+	}
+	conf.UpstreamConfig = &uc
+	return Context.dnsServer.Prepare(conf)
+}
+
 func TestWhois(t *testing.T) {
+	err := prepareTestDNSServer()
+	assert.Nil(t, err)
+
 	w := Whois{timeoutMsec: 5000}
 	resp, err := w.queryAll("8.8.8.8")
 	assert.True(t, err == nil)