lntest: fix most linter warnings, silence rest

We fix all linter issues except for the 'lostcontext' and 'unparam' ones
as those are too numerous and would increase the diff even more.
Therefore we silence them in the itest directory for now.
Because the linter is still not build tag aware, we also have to silence
the unused and deadcode sub linters to not get false positives.

lntest/itest/lnd_rest_api_test.go

@@ -49,9 +49,9 @@ var (
 	resultPattern = regexp.MustCompile("{\"result\":(.*)}")
 )
 
-// testRestApi tests that the most important features of the REST API work
+// testRestAPI tests that the most important features of the REST API work
 // correctly.
-func testRestApi(net *lntest.NetworkHarness, ht *harnessTest) {
+func testRestAPI(net *lntest.NetworkHarness, ht *harnessTest) {
 	testCases := []struct {
 		name string
 		run  func(*testing.T, *lntest.HarnessNode, *lntest.HarnessNode)
@@ -396,6 +396,7 @@ func testRestApi(net *lntest.NetworkHarness, ht *harnessTest) {
 	}
 
 	for _, tc := range testCases {
+		tc := tc
 		ht.t.Run(tc.name, func(t *testing.T) {
 			tc.run(t, net.Alice, net.Bob)
 		})
@@ -486,10 +487,11 @@ func openWebSocket(node *lntest.HarnessNode, url, method string,
 	fullURL := fmt.Sprintf(
 		"wss://%s%s?method=%s", node.Cfg.RESTAddr(), url, method,
 	)
-	conn, _, err := webSocketDialer.Dial(fullURL, header)
+	conn, resp, err := webSocketDialer.Dial(fullURL, header)
 	if err != nil {
 		return nil, err
 	}
+	defer func() { _ = resp.Body.Close() }()
 
 	// Send the given request message as the first message on the socket.
 	reqMsg, err := jsonMarshaler.MarshalToString(req)