add override to GetPollCount() function

test/cpp/qps/client_async.cc

@@ -209,7 +209,7 @@ class AsyncClient : public ClientImpl<StubType, RequestType> {
     }
   }
 
-  int GetPollCount() {
+  int GetPollCount() override {
     int count = 0;
     for (auto cq = cli_cqs_.begin(); cq != cli_cqs_.end(); cq++) {
       count += (int)grpc_get_cq_poll_num((*cq)->cq());

test/cpp/qps/server_async.cc

@@ -158,7 +158,7 @@ class AsyncQpsServerTest final : public grpc::testing::Server {
     shutdown_thread.join();
   }
 
-  int GetPollCount() {
+  int GetPollCount() override {
     int count = 0;
     for (auto cq = srv_cqs_.begin(); cq != srv_cqs_.end(); cq++) {
       count += (int)grpc_get_cq_poll_num((*cq)->cq());