* Change charm to inherit layer:openstack-api as this is an API charm
This adds the SSL config options to the charms config.yaml
* Barbican now servers the API service through Apache so add code
to manage /etc/apache2/conf-available/barbican-api.conf
* Switch BarbicanConfigurationAdapter to be a child of
APIConfigurationAdapter to inherit methods for configuring haproxy
and apache2.
* Add reactive handle to configure ssl when identity relation is
complete
* Move Juno template dir to mitaka as mitaka is the earliest
supported release.
* Updated host_href in barbican.conf to specify the correct external
url for accessing the service. Without this clients are redirected
to the wrong location.