Revert "Fix OSX error and re-merge unhandled exceptions handling (#14…

[rkooo567]

…138)"

This reverts commit ee584e8.

Why are these changes needed?

Related issue number

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• I've run scripts/format.sh to lint the changes in this PR.
• I've included any doc changes needed for https://docs.ray.io/en/master/.
• I've made sure the tests are passing. Note that there might be a few flaky tests, see the recent failures at https://flakey-tests.ray.io/
• Testing Strategy
  • Unit tests
  • Release tests
  • This PR is not tested :(

[ericl]

Thread 15435 (idle): "MainThread"
    syscall (libc-2.27.so)
    absl::lts_2019_08_08::synchronization_internal::Waiter::Wait (ray/_raylet.so)
    AbslInternalPerThreadSemWait (ray/_raylet.so)
    absl::lts_2019_08_08::Mutex::Block (ray/_raylet.so)
    absl::lts_2019_08_08::Mutex::LockSlowLoop (ray/_raylet.so)
    absl::lts_2019_08_08::Mutex::LockSlowWithDeadline (ray/_raylet.so)
    absl::lts_2019_08_08::Mutex::LockSlow (ray/_raylet.so)
    ray::CoreWorkerMemoryStore::GetOrPromoteToPlasma (ray/_raylet.so)
    ray::CoreWorker::PromoteObjectToPlasma (ray/_raylet.so)
    serialize_and_promote_object_ref (ray/_raylet.so)
    object_ref_reducer (ray/serialization.py:91)
    _Pickle_FastCall (_pickle.c:363)
    save (_pickle.c:4417)
    dump (_pickle.c:4527)
    _pickle_Pickler_dump (_pickle.c:4598)
    dump (ray/cloudpickle/cloudpickle_fast.py:588)
    dumps (ray/cloudpickle/cloudpickle_fast.py:73)
    _to_cloudpickle (ray/tune/utils/serialization.py:26)
    default (ray/tune/utils/serialization.py:21)
    _iterencode (json/encoder.py:437)
    _iterencode_dict (json/encoder.py:404)
    _iterencode_dict (json/encoder.py:404)
    _iterencode (json/encoder.py:430)
    encode (json/encoder.py:201)
    dumps (json/__init__.py:238)
    get_json_state (ray/tune/trial.py:604)
    get_checkpoints (ray/tune/trial_executor.py:72)
    _serialize_and_write (ray/tune/trial_runner.py:108)
    checkpoint (ray/tune/trial_runner.py:125)
    checkpoint (ray/tune/trial_runner.py:402)
    run (ray/tune/tune.py:522)
    <module> (pbt_dcgan_mnist_func.py:129)
Thread 15660 (idle): "Dummy-9"
    __pthread_cond_timedwait (libpthread-2.27.so)
    _raylet_unhandled_exception_handler (ray/_raylet.so)
    ray::CoreWorkerMemoryStore::Put (ray/_raylet.so)
    ray::TaskManager::MarkPendingTaskFailed (ray/_raylet.so)
    ray::TaskManager::PendingTaskFailed (ray/_raylet.so)
    std::_Function_handler<void (ray::Status const&, ray::rpc::PushTaskReply const&), ray::CoreWorkerDirectActorTaskSubmitter::PushActorTask(ray::CoreWorkerDirectActorTaskSubmitter::ClientQueue const&, ray::TaskSpecification const&, bool)::{lambda(ray::Status, ray::rpc::PushTaskReply const&)#1}>::_M_invoke (ray/_raylet.so)
    std::_Function_handler<void (ray::Status const&, ray::rpc::PushTaskReply const&), ray::rpc::CoreWorkerClient::SendRequests()::{lambda(ray::Status, ray::rpc::PushTaskReply const&)#1}>::_M_invoke (ray/_raylet.so)
    ray::rpc::ClientCallImpl<ray::rpc::PushTaskReply>::OnReplyReceived (ray/_raylet.so)
    boost::asio::detail::completion_handler<ray::rpc::ClientCallManager::PollEventsFromCompletionQueue(int)::{lambda()#1}>::do_complete (ray/_raylet.so)
    boost::asio::detail::scheduler::do_run_one (ray/_raylet.so)
    boost::asio::detail::scheduler::run (ray/_raylet.so)
    boost::asio::io_context::run (ray/_raylet.so)
    ray::CoreWorker::RunIOService (ray/_raylet.so)
    0x7fd6d7e3e66f (libstdc++.so.6.0.25)