Add posibility to configure the API to service requests via HTTPS instead
of HTTP using native ssl from oslo.service wsgi.
New options was added:
* enable_ssl_api - turn on ssl support;
Options defined in oslo.service for configure certs:
* ca_file - ca certificate file to use to verify connecting clients;
* cert_file - certificate file to use when starting the server securely;
* key_file - private key file to use when starting the server securely;
Closes-bug: #1430213
Change-Id: Id4b84d83f9aa6c7f898b3b9b59158d5b1a00e159
564f5f7cd7