Merge: * set BlockingMode: "null_ip" by default; minor improvements

Squashed commit of the following:

commit 653544b98dc4d1b9a74e1509d0e6104b71bcdcb3
Author: Simon Zolin <s.zolin@adguard.com>
Date:   Wed Dec 11 17:34:41 2019 +0300

    * DNS reconfigure: protect against delayed socket fd close

commit 9e650f37dee7f771bf1d9d714c35f0a81788aa16
Author: Simon Zolin <s.zolin@adguard.com>
Date:   Wed Dec 11 15:28:33 2019 +0300

    - fix race on startup

commit 878fdb8fc4ebbc6fab683a65f5e4298e64c2073e
Author: Simon Zolin <s.zolin@adguard.com>
Date:   Wed Dec 11 15:11:21 2019 +0300

    * travis: don't run tests

commit 1c4ab60684ee22d55e6d2a3350c0f24d9844255c
Author: Simon Zolin <s.zolin@adguard.com>
Date:   Wed Dec 11 14:56:28 2019 +0300

    * travis: 'release.sh' and then run tests

commit e1f644b8d9a1f3b46990cdfb1b75fd81b3a49d33
Author: Simon Zolin <s.zolin@adguard.com>
Date:   Wed Dec 11 14:52:59 2019 +0300

    * set BlockingMode: "null_ip" by default

.travis.yml

@@ -42,8 +42,6 @@ matrix:
       script:
         - node -v
         - npm -v
-        # Run tests just in case
-        - go test -race -v -bench=. ./...
         # Prepare releases
         - ./release.sh
         - ls -l dist

dnsforward/dnsforward.go

@@ -360,10 +360,9 @@ func (s *Server) Reconfigure(config *ServerConfig) error {
 		return errorx.Decorate(err, "could not reconfigure the server")
 	}
 
-	// On some Windows versions the UDP port we've just closed in proxy.Stop() doesn't get actually closed right away.
+	// It seems that net.Listener.Close() doesn't close file descriptors right away.
-	if runtime.GOOS == "windows" {
+	// We wait for some time and hope that this fd will be closed.
-		time.Sleep(1 * time.Second)
+	time.Sleep(100 * time.Millisecond)
-	}
 
 	err = s.Prepare(config)
 	if err != nil {

home/config.go

@@ -158,7 +158,7 @@ var config = configuration{
 		StatsInterval: 1,
 		FilteringConfig: dnsforward.FilteringConfig{
 			ProtectionEnabled:  true,      // whether or not use any of dnsfilter features
-			BlockingMode:       "nxdomain", // mode how to answer filtered requests
+			BlockingMode:       "null_ip", // mode how to answer filtered requests
 			BlockedResponseTTL: 10,        // in seconds
 			Ratelimit:          20,
 			RefuseAny:          true,

home/home.go

@@ -172,7 +172,7 @@ func run(args options) {
 			log.Fatalf("%s", err)
 		}
 		go func() {
-			err = startDNSServer()
+			err := startDNSServer()
 			if err != nil {
 				log.Fatal(err)
 			}