create_client should return a way to close the protocol.
create_client should return a way to close the protocol.

Summary:
This is to avoid a pending task warning on program exit.

I updated all the callers of this to accept the new behavior

Test Plan: fbpkg.par build -E fbpkg

Reviewed By: dtw@fb.com

Subscribers: ruibalp, alandau, bmatheny, yfeldblum, dpittman

FB internal diff: D2372394

Tasks: 8099974

Signature: t1:2372394:1441050027:1d1b52fe49eaed65e0636b8b6e4d25476e5062d8

LinusU/fbthrift,sinjar666/fbthrift,SergeyMakarenko/fbthrift,SergeyMakarenko/fbthrift,getyourguide/fbthrift,facebook/fbthrift,sinjar666/fbthrift,Orvid/fbthrift,Orvid/fbthrift,SergeyMakarenko/fbthrift,Orvid/fbthrift,getyourguide/fbthrift,SergeyMakarenko/fbthrift,getyourguide/fbthrift,sinjar666/fbthrift,getyourguide/fbthrift,Orvid/fbthrift,sinjar666/fbthrift,Orvid/fbthrift,getyourguide/fbthrift,sinjar666/fbthrift,SergeyMakarenko/fbthrift,LinusU/fbthrift,LinusU/fbthrift,getyourguide/fbthrift,facebook/fbthrift,Orvid/fbthrift,SergeyMakarenko/fbthrift,facebook/fbthrift,Orvid/fbthrift,SergeyMakarenko/fbthrift,sinjar666/fbthrift,getyourguide/fbthrift,getyourguide/fbthrift,LinusU/fbthrift,SergeyMakarenko/fbthrift,getyourguide/fbthrift,getyourguide/fbthrift,sinjar666/fbthrift,sinjar666/fbthrift,getyourguide/fbthrift,facebook/fbthrift,facebook/fbthrift,sinjar666/fbthrift,Orvid/fbthrift,SergeyMakarenko/fbthrift,Orvid/fbthrift,Orvid/fbthrift,facebook/fbthrift,LinusU/fbthrift,LinusU/fbthrift,LinusU/fbthrift,LinusU/fbthrift,LinusU/fbthrift,facebook/fbthrift,LinusU/fbthrift,facebook/fbthrift,facebook/fbthrift,sinjar666/fbthrift,Orvid/fbthrift,SergeyMakarenko/fbthrift,sinjar666/fbthrift,SergeyMakarenko/fbthrift,SergeyMakarenko/fbthrift,getyourguide/fbthrift,LinusU/fbthrift