2089 fix restart runtime error

Tested with unittest and latest reproducer in bug.

```
root@precise64:/vagrant# ID=$(docker run -d busybox sleep 60)
root@precise64:/vagrant# invoke-rc.d docker restart
invoke-rc.d: unknown initscript, /etc/init.d/docker not found.
root@precise64:/vagrant# docker kill $ID
68cfb88cf047
root@precise64:/vagrant# docker start $ID
68cfb88cf047
root@precise64:/vagrant# docker ps
ID                  IMAGE               COMMAND             CREATED             STATUS              PORTS
68cfb88cf047        busybox:latest      sleep 60            10 seconds ago      Up 8 seconds
```