`docker cp` error when container doesn't exist

Fix cp api to return a 404 notfound if container doesn't exist.
Fixes #4119.

Docker-DCO-1.1-Signed-off-by: Fabio Falci <fabiofalci@gmail.com> (github: fabiofalci)
Add dockerode NodeJS implementation
Also correctly case 'JavaScript'

Docker-DCO-1.1-Signed-off-by: Mike MacCana <mike.maccana@gmail.com> (github: mikemaccana)
Merge pull request #4061 from mikemaccana/patch-1

Add dockerode NodeJS implementation
Merge pull request #4164 from fabiofalci/cp_error_message

`docker cp` error when container doesn't exist
Add systemd:systemd-nspawn plugin
systemd-nspawn execdriver

  Allowing the docker daemon to use alternate to lxc execdriver.
  By starting as: EXEC_DRIVER=systemd docker -d
  or setting the variable in /etc/default/docker

Docker-DCO-1.1-Signed-off-by: Vincent Batts <vbatts@redhat.com> (github: vbatts)