message: Remove duplicate hash table lookups in grpc_eager_client.
diff: @@ -100,7 +100,7 @@ class GrpcEagerClient : public EagerClient {
  const auto& it = enqueue_dispatchers_.find(request->context_id());
  if (it != enqueue_dispatchers_.end()) {
  it->second.CancelCall();
  - enqueue_dispatchers_.erase(request->context_id());
  + enqueue_dispatchers_.erase(it);
  } else if (EnableStreaming()) {
  LOG(ERROR) << "Remote EagerContext with id " << request->context_id()
  << " does not seem to exist.";
  @@ -113,8 +113,7 @@ class GrpcEagerClient : public EagerClient {
  if (EnableStreaming()) {
  tf_shared_lock l(mu_);
  auto it = enqueue_dispatchers_.find(request->context_id());
  - if (enqueue_dispatchers_.find(request->context_id()) ==
  - enqueue_dispatchers_.end()) {
  + if (it == enqueue_dispatchers_.end()) {
  auto it_and_bool = enqueue_dispatchers_.emplace(
  std::piecewise_construct,
  std::forward_as_tuple(request->context_id()),
  