Revert "fix(server): Disable CN check (Go 15 does not support). Fixes a…

…rgoproj#5539 (argoproj#5550)"

This reverts commit 20f0047.

server/apiserver/argoserver.go

@@ -16,6 +16,7 @@ import (
 	"github.com/soheilhy/cmux"
 	"golang.org/x/net/context"
 	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials"
 	"k8s.io/apimachinery/pkg/util/wait"
 	"k8s.io/client-go/rest"
 
@@ -271,8 +272,13 @@ func (as *argoServer) newHTTPServer(ctx context.Context, port int, artifactServe
 	}
 	dialOpts := []grpc.DialOption{
 		grpc.WithDefaultCallOptions(grpc.MaxCallRecvMsgSize(MaxGRPCMessageSize)),
-		grpc.WithInsecure(),
 	}
+	if as.tlsConfig != nil {
+		dialOpts = append(dialOpts, grpc.WithTransportCredentials(credentials.NewTLS(as.tlsConfig)))
+	} else {
+		dialOpts = append(dialOpts, grpc.WithInsecure())
+	}
+
 	webhookInterceptor := webhook.Interceptor(as.clients.Kubernetes)
 
 	// HTTP 1.1+JSON Server