Add support for eventlet in GRPC

[Akrog]

Google's GRPC python library doesn't work with eventlet out of the box.
Ember-CSI has a workaround for it for non stream connections.
It would be best to create a proper fix for the grpc Python library to add support for eventlet and remove the workaround from our code, as this would ensure that new versions of the library would not break us.