Pull request: 2846 cover aghnet vol.4

Merge in DNS/adguard-home from 2846-cover-aghnet-vol.4 to master

Updates #2846.

Squashed commit of the following:

commit 576ef857628a403ce1478c10a4aad23985c09613
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Thu Mar 31 19:38:57 2022 +0300

    aghnet: imp code

commit 5b4b17ff52867aaab2c9d30a0fc7fc2fe31ff4d5
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Thu Mar 31 14:58:34 2022 +0300

    aghnet: imp coverage

internal/aghnet/net_openbsd.go

@@ -13,10 +13,6 @@ import (
 	"github.com/AdguardTeam/AdGuardHome/internal/aghos"
 )
 
-func canBindPrivilegedPorts() (can bool, err error) {
-	return aghos.HaveAdminRights()
-}
-
 func ifaceHasStaticIP(ifaceName string) (ok bool, err error) {
 	filename := fmt.Sprintf("etc/hostname.%s", ifaceName)