message: fix possible conflix between BGSave and DBSync
diff: @@ -844,6 +844,13 @@ bool PikaServer::InitBgsaveEngine() {
  }
  bool PikaServer::RunBgsaveEngine(const std::string path) {
  + // Prepare for Bgsaving
  + if (!InitBgsaveEnv() || !InitBgsaveEngine()) {
  + ClearBgsave();
  + return false;
  + }
  + LOG(INFO) << "after prepare bgsave";
  +
  // Backup to tmp dir
  nemo::Status nemo_s = bgsave_engine_->CreateNewBackup(path);
  LOG(INFO) << "Create new backup finished.";
  @@ -865,13 +872,6 @@ void PikaServer::Bgsave() {
  bgsave_info_.bgsaving = true;
  }
  - // Prepare for Bgsaving
  - if (!InitBgsaveEnv() || !InitBgsaveEngine()) {
  - ClearBgsave();
  - return;
  - }
  - LOG(INFO) << "after prepare bgsave";
  -
  // Start new thread if needed
  bgsave_thread_.StartThread();
  bgsave_thread_.Schedule(&DoBgsave, static_cast<void*>(this));
  