Merge pull request #16880 from grpc/revert-16841-add_cpp_gcd_to_cloud_to_prod_auth

Revert "Add c++ google default creds to cloud to prod auth scenarios"

test/cpp/interop/client.cc

@@ -137,8 +137,7 @@ int main(int argc, char** argv) {
       &grpc::testing::InteropClient::DoTimeoutOnSleepingServer, &client);
   actions["empty_stream"] =
       std::bind(&grpc::testing::InteropClient::DoEmptyStream, &client);
-  if (FLAGS_use_tls ||
-      FLAGS_custom_credentials_type == "google_default_credentials") {
+  if (FLAGS_use_tls) {
     actions["compute_engine_creds"] =
         std::bind(&grpc::testing::InteropClient::DoComputeEngineCreds, &client,
                   FLAGS_default_service_account, FLAGS_oauth_scope);

tools/run_tests/run_interop_tests.py

@@ -1378,8 +1378,7 @@ try:
                                 transport_security='tls')
                             jobs.append(tls_test_job)
                             if str(language) in [
-                                    'c++',
-                                    'go',
+                                    'go'
                             ]:  # Add more languages to the list to turn on tests.
                                 google_default_creds_test_job = cloud_to_prod_jobspec(
                                     language,