message: [SE] Avoid deadlock by calling HostCallbacks even when the stream is in an error state
  HostCallbacks may trigger notifications that, if elided, would cause programs to hang. Ideally we would have errback semantics, but this is a band-aid while the semantics are redefined.
diff: @@ -5287,12 +5287,11 @@ Stream &Stream::ThenTransformTensor(const dnn::BatchDescriptor &input_desc,
  Stream &Stream::ThenDoHostCallback(std::function<void()> callback) {
  VLOG_CALL(PARAM(callback));
  - if (ok()) {
  - CheckError(parent_->HostCallback(this, callback));
  - } else {
  + if (!ok()) {
  LOG(INFO) << DebugStreamPointers()
  << " was in error state before adding host callback";
  }
  + CheckError(parent_->HostCallback(this, std::move(callback)));
  return *this;
  }
  @@ -5300,12 +5299,11 @@ Stream &Stream::ThenDoHostCallbackWithStatus(
  std::function<port::Status()> callback) {
  VLOG_CALL(PARAM(callback));
  - if (ok()) {
  - CheckError(parent_->HostCallback(this, std::move(callback)));
  - } else {
  - LOG(WARNING) << "stream " << DebugStreamPointers()
  + if (!ok()) {
  + LOG(INFO) << DebugStreamPointers()
  << " was in error state before adding host callback";
  }
  + CheckError(parent_->HostCallback(this, std::move(callback)));
  return *this;
  }
  