dial-stdio: Close the connection
dial-stdio: Close the connection

This was leaking the fd.

Signed-off-by: Ian Campbell <a8db091655a7f47ecb9c39a2d278e9662e440dc0@docker.com>

docker/cli,cpuguy83/cli,cpuguy83/cli,docker/cli,thaJeztah/cli,thaJeztah/cli