message: fix removing of file
  use try_remove instead of exists+remove to better handle removing a non existing file without crashing the process
diff: @@ -211,9 +211,7 @@ void GlobalNotifier::Impl::release_version(sync::ObjectID id, VersionID old_vers
  if (info.coordinator) {
  std::string path = info.coordinator->get_config().path;
  m_realms.erase(it);
  - if (File::exists(path)) {
  - File::remove(path);
  - }
  + File::try_remove(path);
  }
  else {
  m_realms.erase(it);
  