message: Let HloModule::Clone("") preserve the cloned name.
diff: @@ -559,7 +559,8 @@ std::unique_ptr<HloModule> HloModule::Clone(const string& suffix) const {
  std::unique_ptr<HloModule> HloModule::Clone(const HloModuleConfig& config,
  const string& suffix) const {
  VLOG(1) << "Cloning module :" << name_ << " --> " << suffix << "\n";
  - auto module = absl::make_unique<HloModule>(name_ + "-" + suffix, config);
  + auto module = absl::make_unique<HloModule>(
  + absl::StrCat(name_, suffix.empty() ? "" : "-", suffix), config);
  HloCloneContext context(module.get(), suffix);
  auto cloned_computation = entry_computation_->Clone(suffix, &context);
  