dns: fix data race in TestDNS_ServiceLookup_FilterACL

The agent config cannot be modified after start.

agent/dns_test.go

@@ -3615,7 +3615,17 @@ func TestDNS_ServiceLookup_SRV_RFC_TCP_Default(t *testing.T) {
 
 func TestDNS_ServiceLookup_FilterACL(t *testing.T) {
 	t.Parallel()
+	tests := []struct {
+		token   string
+		results int
+	}{
+		{"root", 1},
+		{"anonymous", 0},
+	}
+	for _, tt := range tests {
+		t.Run("ACLToken == "+tt.token, func(t *testing.T) {
 			cfg := TestConfig()
+			cfg.ACLToken = tt.token
 			cfg.ACLMasterToken = "root"
 			cfg.ACLDatacenter = "dc1"
 			cfg.ACLDownPolicy = "deny"
@@ -3645,24 +3655,14 @@ func TestDNS_ServiceLookup_FilterACL(t *testing.T) {
 			m := new(dns.Msg)
 			m.SetQuestion("foo.service.consul.", dns.TypeA)
 
-	// Query with the root token. Should get results.
-	a.Config.ACLToken = "root"
 			in, _, err := c.Exchange(m, addr.String())
 			if err != nil {
 				t.Fatalf("err: %v", err)
 			}
-	if len(in.Answer) != 1 {
+			if len(in.Answer) != tt.results {
 				t.Fatalf("Bad: %#v", in)
 			}
-
+		})
-	// Query with a non-root token without access. Should get nothing.
-	a.Config.ACLToken = "anonymous"
-	in, _, err = c.Exchange(m, addr.String())
-	if err != nil {
-		t.Fatalf("err: %v", err)
-	}
-	if len(in.Answer) != 0 {
-		t.Fatalf("Bad: %#v", in)
 	}
 }