Pull request:* all: fix all staticcheck simplification and unused warnings

Merge in DNS/adguard-home from 2270-fix-s-u-warnings to master

Squashed commit of the following:

commit 03e0f78bd471057007c2d4042ee26eda2bbc9b29
Merge: 50dc3ef5c 7e16fda57
Author: Eugene Burkov <e.burkov@adguard.com>
Date:   Fri Nov 6 11:54:09 2020 +0300

    Merge branch 'master' into 2270-fix-s-u-warnings

commit 50dc3ef5c44a5fdc941794c26784b0c44d7b5aa0
Author: Eugene Burkov <e.burkov@adguard.com>
Date:   Thu Nov 5 19:48:54 2020 +0300

    * all: improve code quality

commit d6d804f759ce3e47154a389b427550e72c4b9090
Author: Eugene Burkov <e.burkov@adguard.com>
Date:   Thu Nov 5 18:03:35 2020 +0300

    * all: fix all staticcheck simplification and unused warnings

    Closes #2270.

internal/dhcpd/network_utils.go

@@ -73,7 +73,6 @@ func hasStaticIPDhcpcdConf(dhcpConf, ifaceName string) bool {
 				// we found our interface
 				withinInterfaceCtx = true
 			}
-
 		} else {
 			if strings.HasPrefix(line, "interface ") {
 				// we found another interface - reset our state
@@ -240,7 +239,7 @@ func getNetworkSetupHardwareReports() map[string]string {
 		return nil
 	}
 
-	m := make(map[string]string, 0)
+	m := make(map[string]string)
 
 	matches := re.FindAllStringSubmatch(out, -1)
 	for i := range matches {