grpc 运行中报g_state != nullptr 的问题

Spent few days chasing down this issue, and it might potentially cause a lot of pain to TensorFlow users. All TensorFlow operators implemented in C++ are built as a shared libraries like this one: https://github.com/tensorflow/io/blob/master/tensorflow_io/bigquery/BUILD
Whenever 2 different libraries using grpc and loaded into one process, calls to grpc::CreateChannel in a library that is loaded second will fail. For users it is going to look like some working code started crashing, and such issue is going to be pretty hard to debug.