This makes the docker cli reject docker run commands which include bind
mounts like "/:/some/path/in/the/container".
Bind mounting the root directory is a bad idea and the cli should throw
an error right away.
The same check will also be made by the remote API via another commit.
Upstream-commit: 4b8c41c4a2591797f97ad079e4314b21498ba732
Component: engine