Remove requirement for custom RPCClient (#5405)

This change is a simplification over existing
code since it is not required to have a separate
RPCClient structure instead keep authRPCClient can
do the same job.

There is no code which directly uses netRPCClient(),
keeping authRPCClient is better and simpler. This
simplication also allows for removal of multiple
levels of locking code per object.

Observed in #5160

cmd/rpc-server_test.go

@@ -19,6 +19,7 @@ package cmd
 import (
 	"net/http"
 	"net/http/httptest"
+	"os"
 	"testing"
 
 	router "github.com/gorilla/mux"
@@ -32,10 +33,11 @@ type ArithReply struct {
 	C int
 }
 
-type Arith int
+type Arith struct {
+	AuthRPCServer
+}
 
 // Some of Arith's methods have value args, some have pointer args. That's deliberate.
-
 func (t *Arith) Add(args ArithArgs, reply *ArithReply) error {
 	reply.C = args.A + args.B
 	return nil
@@ -43,7 +45,9 @@ func (t *Arith) Add(args ArithArgs, reply *ArithReply) error {
 
 func TestGoHTTPRPC(t *testing.T) {
 	newServer := newRPCServer()
-	newServer.Register(new(Arith))
+	newServer.Register(&Arith{
+		AuthRPCServer: AuthRPCServer{},
+	})
 
 	mux := router.NewRouter().SkipClean(true)
 	mux.Path("/foo").Handler(newServer)
@@ -51,13 +55,30 @@ func TestGoHTTPRPC(t *testing.T) {
 	httpServer := httptest.NewServer(mux)
 	defer httpServer.Close()
 
-	client := newRPCClient(httpServer.Listener.Addr().String(), "/foo", false)
+	rootPath, err := newTestConfig("us-east-1")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(rootPath)
+
+	creds := globalServerConfig.GetCredential()
+	client := newAuthRPCClient(authConfig{
+		serverAddr:      httpServer.Listener.Addr().String(),
+		serviceName:     "Arith",
+		serviceEndpoint: "/foo",
+		accessKey:       creds.AccessKey,
+		secretKey:       creds.SecretKey,
+	})
 	defer client.Close()
 
+	if err = client.Login(); err != nil {
+		t.Fatal(err)
+	}
+
 	// Synchronous calls
 	args := &ArithArgs{7, 8}
 	reply := new(ArithReply)
-	if err := client.Call("Arith.Add", args, reply); err != nil {
+	if err = client.rpcClient.Call("Arith.Add", args, reply); err != nil {
 		t.Errorf("Add: expected no error but got string %v", err)
 	}