Fixing the error message.

src/core/ext/filters/client_channel/xds/xds_channel.cc

@@ -32,7 +32,8 @@ grpc_channel* CreateXdsChannel(const XdsBootstrap& bootstrap,
                                const grpc_channel_args& args,
                                grpc_error** error) {
   if (!bootstrap.server().channel_creds.empty()) {
-    *error = GRPC_ERROR_CREATE_FROM_STATIC_STRING("no credential found");
+    *error = GRPC_ERROR_CREATE_FROM_STATIC_STRING(
+        "credential specified but gRPC not built with security");
     return nullptr;
   }
   return grpc_insecure_channel_create(bootstrap.server().server_uri.c_str(),