We decided to deprecated NovaDocker driver in the team meeting [1].
Therefore, we moved the driver to the contrib folder. NovaDocker
was an experimental driver that attempts to leverage Nova to provide
networking to containers. However, as kuryr integration implemented,
this driver is not needed anymore.
[1] http://eavesdrop.openstack.org/meetings/zun/2017/
zun.2017-07-11-03.00.log.html
Change-Id: I770fe13a004dc56ad20fe8eca545f05c4504e48e
6dc2866167