Fix a race condition in ParallelStreamWriter.
Fix a race condition in ParallelStreamWriter.

Signed-off-by: Matthieu Nottale <265791a9b5c879da44c284b411d2ec13b4d977b5@docker.com>

dnephin/compose,thaJeztah/compose,dnephin/compose,shin-/compose,shin-/compose,vdemeester/compose,funkyfuture/docker-compose,thaJeztah/compose,vdemeester/compose,funkyfuture/docker-compose