add test and move one from rm to rmi

test for ##8368
They is no way to do that:

`err` is `exit status 1` (it's the error from the client)
`output` is `Error response from daemon: No such container: unknown\n2014/10/06 17:12:08 Error: failed to remove one or more containers\n` (with the date inside, so it's painful to test)

Either we merge this, or I close it :D