Pull request 1948: imp-test

Squashed commit of the following:

commit d2e61b0a2406a503d9d7bcd12612ed7e04c1fac6
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Tue Aug 1 18:02:29 2023 +0300

    client: imp addrproc test

commit f7cf0fb1549299b00fdbe400bb4a96c73530bfe0
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Tue Aug 1 17:23:12 2023 +0300

    dnsforward: rm mutex

internal/dnsforward/dnsforward_test.go

@@ -72,13 +72,6 @@ func startDeferStop(t *testing.T, s *Server) {
 	testutil.CleanupAndRequireSuccess(t, s.Stop)
 }
 
-// packageUpstreamVariableMu is used to serialize access to the package-level
-// variables of package upstream.
-//
-// TODO(s.chzhen): Move these parameters to upstream options and remove this
-// crutch.
-var packageUpstreamVariableMu = &sync.Mutex{}
-
 func createTestServer(
 	t *testing.T,
 	filterConf *filtering.Config,
@@ -87,9 +80,6 @@ func createTestServer(
 ) (s *Server) {
 	t.Helper()
 
-	packageUpstreamVariableMu.Lock()
-	defer packageUpstreamVariableMu.Unlock()
-
 	rules := `||nxdomain.example.org
 ||NULL.example.org^
 127.0.0.1	host.example.org