fix unittest failure

Former-commit-id: 9707d5d7550b9db72b4bbdd5c71f6e68febdb36d

cpp/unittest/db/utils.cpp

@@ -12,6 +12,7 @@
 #include "utils.h"
 #include "db/Factories.h"
 #include "db/Options.h"
+#include "server/ServerConfig.h"
 
 INITIALIZE_EASYLOGGINGPP
 
@@ -60,6 +61,9 @@ engine::Options DBTest::GetOptions() {
 void DBTest::SetUp() {
     InitLog();
 
+    server::ConfigNode& config = server::ServerConfig::GetInstance().GetConfig(server::CONFIG_CACHE);
+    config.AddSequenceItem(server::CONFIG_GPU_IDS, "0");
+
     auto res_mgr = engine::ResMgrInst::GetInstance();
     res_mgr->Clear();
     res_mgr->Add(engine::ResourceFactory::Create("disk", "DISK", 0, true, false));