This sets firewall rules for elasticsearch to listen on
9200/TCP via the es_listen_external: true directive.
Additionally upstream nginx seems to have change their config
directory layout so /etc/nginx/conf.d/ is no longer the default,
we still want to use this so it's now created if it doesn't
exist.
Fixes bug 1605721
Fixes bug 1605722
Patchset #3: rename groupvars variable to es_listen_external
Change-Id: I3dcfd36a9836412f326d6af0d38ea2e2a0e01303
7d23123155