Run nginx for SSL and load-balancing.

Purpose:
  Enable SSL on all endpoints for security, and
  load-balance all endpoints for availability.

Changes:
  - run nginx on all controller nodes
  - monitor nginx processes with sensu
  - pull ssl cert and key from vars, install to /etc/nginx/ssl
  - configure an 'openstack' nginx site
  - add nginx endpoints to front horizon and all api services
  - install cert to system /etc/ssl/certs
  - make CA cert available under /opt/stack/ssl
  - setup default /root/stackrc to trust the cert
  - update keystone service catalog to use new endpoints
  - redirect horizon on port 80 to 443

TODO:
  - use upstream { ... } to point each nginx to every
    controller.
Merge pull request #16 from blueboxgroup/nginx

WIP: Run nginx for SSL and load-balancing.
Remove stale TODO from example config.
Point to ssl cert when setting up neutron nets/subnets.
Add openstack cert to httplib2's cacerts.txt.

neutron-metadata-agent was failing to talk to nova
after the introduction of ssl endpoints because httplib2,
which neutronclient depends on, ships with it's own cacerts.txt,
instead of using the system one in /etc/ssl.
Merge remote-tracking branch 'origin/master' into openstack-ha