Fix py.asyncio tutorial client
Fix py.asyncio tutorial client

Summary:
Client is exiting with pending coroutines. Closing
the transport and loop properly solves this.

Reviewed By: dresende

Differential Revision: D2913227

fb-gh-sync-id: 9ef86b6d6517ecfb79664164b55b6d39f6185d0e

SergeyMakarenko/fbthrift,facebook/fbthrift,getyourguide/fbthrift,getyourguide/fbthrift,LinusU/fbthrift,SergeyMakarenko/fbthrift,SergeyMakarenko/fbthrift,getyourguide/fbthrift,LinusU/fbthrift,getyourguide/fbthrift,LinusU/fbthrift,getyourguide/fbthrift,LinusU/fbthrift,LinusU/fbthrift,SergeyMakarenko/fbthrift,facebook/fbthrift,facebook/fbthrift,getyourguide/fbthrift,LinusU/fbthrift,getyourguide/fbthrift,SergeyMakarenko/fbthrift,getyourguide/fbthrift,getyourguide/fbthrift,LinusU/fbthrift,SergeyMakarenko/fbthrift,getyourguide/fbthrift,LinusU/fbthrift,SergeyMakarenko/fbthrift,facebook/fbthrift,facebook/fbthrift,LinusU/fbthrift,facebook/fbthrift,SergeyMakarenko/fbthrift,facebook/fbthrift,SergeyMakarenko/fbthrift,facebook/fbthrift,SergeyMakarenko/fbthrift,SergeyMakarenko/fbthrift,LinusU/fbthrift,SergeyMakarenko/fbthrift,LinusU/fbthrift,getyourguide/fbthrift,facebook/fbthrift,getyourguide/fbthrift