Remove dependency on lxc-attach

[jsdir]

agent.autoload

def autoload(instance_id, app_path):
    # Check for user-defined autoload.sh
    # TODO: In a newer release, docker will have functionality to run
    #       a command inside a running container. This will remove
    #       dependency of lxc-attach.
    container = Container(instance_id)
    autoload_file = '/usr/share/stretch/autoload.sh'
    code = call(['lxc-attach', '-n', container.id, '--', '/bin/bash',
                 autoload_file])
    if code == 3:
        # No user-defined autoload.sh, restart container
        container.restart()

Docker provides this functionality in a future release. Switch when stable.