Pull request: 3184 disable private ptr

Merge in DNS/adguard-home from 3184-disable-ptr to master

Updates #3184.

Squashed commit of the following:

commit b78ac2eeb1b408586808ddbd1c87107f373b11b0
Author: Eugene Burkov <e.burkov@adguard.com>
Date:   Wed May 26 17:20:34 2021 +0300

    all: rename dns config field

commit 36512134822a5f6b8b296ccbd7e7d5a9b8e87f26
Author: Ildar Kamalov <ik@adguard.com>
Date:   Wed May 26 15:55:44 2021 +0300

    client: handle local ips rdns

commit 9a691830d45db93e078332d85bc0efa7dc7b6ac6
Author: Eugene Burkov <e.burkov@adguard.com>
Date:   Wed May 26 14:43:13 2021 +0300

    all: imp naming

commit 771b7a3d5d25f91408dd97ba3287efb641028ccf
Author: Eugene Burkov <e.burkov@adguard.com>
Date:   Wed May 26 14:24:38 2021 +0300

    all: imp docs, code

commit be960893e8bbb7375a944ca0345b50c857a2d7cf
Author: Eugene Burkov <e.burkov@adguard.com>
Date:   Wed May 26 13:23:56 2021 +0300

    all: imp docs & log changes

commit 4e645a520f6bb584ef951435ee833ad30769af98
Author: Eugene Burkov <e.burkov@adguard.com>
Date:   Wed May 26 12:49:44 2021 +0300

    all: add the field into structs

commit 22b5b6163f086560a3189234532ba877be7ba940
Author: Eugene Burkov <e.burkov@adguard.com>
Date:   Tue May 25 15:10:31 2021 +0300

    dnsforward: entitle lock, imp code

internal/dnsforward/stats.go

@@ -25,7 +25,9 @@ func processQueryLogsAndStats(ctx *dnsContext) (rc resultCode) {
 		shouldLog = false
 	}
 
-	s.RLock()
+	s.serverLock.RLock()
+	defer s.serverLock.RUnlock()
+
 	// Synchronize access to s.queryLog and s.stats so they won't be suddenly uninitialized while in use.
 	// This can happen after proxy server has been stopped, but its workers haven't yet exited.
 	if shouldLog && s.queryLog != nil {
@@ -61,7 +63,6 @@ func processQueryLogsAndStats(ctx *dnsContext) (rc resultCode) {
 	}
 
 	s.updateStats(ctx, elapsed, *ctx.result)
-	s.RUnlock()
 
 	return resultCodeSuccess
 }