This changes the namespace configuration on the config to include the
name of the namespace along with an optional path. This path is used to
point to a file of another namespace for the namespace so that it can be
joined in place of the empty, initialized namespace.
Signed-off-by: Michael Crosby <crosbymichael@gmail.com>
Also add unit test for container json files to ensure that the mount
config is read and device nodes are validated.
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@docker.com> (github: crosbymichael)