message: elle.reactor: clean up
  Tracking some ubsan issue.
diff: @@ -24,7 +24,7 @@ ELLE_LOG_COMPONENT("elle.reactor.Scheduler");
  namespace
  {
  - auto const DBG = elle::os::inenv("REACTOR_SCHEDULER_DEBUG");
  + auto const DBG = elle::os::getenv("REACTOR_SCHEDULER_DEBUG", false);
  }
  namespace elle
  @@ -87,8 +87,8 @@ namespace elle
  auto&
  _schedulers()
  {
  - static std::unordered_map<std::thread::id, Scheduler*> map;
  - return map;
  + static auto res = std::unordered_map<std::thread::id, Scheduler*>{};
  + return res;
  }
  std::mutex&
  