Description of problem:
When you execute `docker attach` on a container, which is in the process of shutting down, the process doesn't fail, but hangs for ever.

Even when you remove (`docker rm`) the container afterwards, the process still exists and when you use eg. ctrl+c, it complains about missing container.

When you have stdin attached, it finishes after an input, otherwise you have to use `kill -9` to get rid of it.

Version-Release number of selected component (if applicable):
docker-0.11.1-10.el7.x86_64
docker-io-1.0.0-3.fc20.x86_64

How reproducible:
rarely on RHEL7 (0.11.1), always on Fedora 20 (1.0.0-3)

Steps to Reproduce:
1. in 1st terminal execute: "while :; do sudo docker -D attach  `sudo docker ps -l -q`; done"
2a. in 2nd terminal execute: "docker run -i -t fedora bash" and when the first terminal attaches, use `exit` or `ctrl+d` to stop the container.
2b. when the 2a doesn't causes the bug, use this script to start-stop containers in a loop: "while :; do ID=`docker run -d -i -t fedora bash`; sleep 1; echo exit | docker attach $ID; done"

Actual results:
On Fedora after step 2a the attach process in 1st terminal hangs, there is no new input.
On RHEL after a while while executing the 2b script, the attach process in 1st terminal hangs.

Expected results:
The attach process in 1st terminal should finish when the container is destroyed and lots of messages like:

2014/06/26 15:29:55 You cannot attach to a stopped container, start it first
2014/06/26 15:29:55 You cannot attach to a stopped container, start it first
2014/06/26 15:29:55 You cannot attach to a stopped container, start it first
2014/06/26 15:29:55 You cannot attach to a stopped container, start it first

should occur (as we are trying to attach stopped container).


Additional info:
When you use `docker attach --no-stdin ...` you can write anything. After a ctrl+c it realizes the container is not running and finishes. ctrl+p+q doesn't work. In RHEL version when you remove the container by `docker rm` first, ctrl+c generates message in docker daemon, that the container with id ... doesn't exist and the `docker attach` process is still hanged.

When you have stdin attached, after sending any character the process is destoyed with:
[debug] hijack.go:96 [hijack] End of stdout
                                           2014/06/26 15:49:31 You cannot attach to a stopped container, start it first