nova-net: Remove 'nova-network' binary

Get excited, people. It's finally dying, for real. There is a lot more
doc work needed here, but this is a start. No need for a release note
modification since we've already said that nova-network has been
removed, so there's no point in saying that the service itself has been
removed since that's implicit.

Change-Id: I18d73212f9d98bc75974a024cf6fd872fdfb1ca4
Signed-off-by: Stephen Finucane <sfinucan@redhat.com>

setup.cfg

@@ -67,7 +67,6 @@ console_scripts =
     nova-compute = nova.cmd.compute:main
     nova-conductor = nova.cmd.conductor:main
     nova-manage = nova.cmd.manage:main
-    nova-network = nova.cmd.network:main
     nova-novncproxy = nova.cmd.novncproxy:main
     nova-policy = nova.cmd.policy:main
     nova-rootwrap = oslo_rootwrap.cmd:main