This patch implements the use of uWSGI exclusively,
always with a web server acting as a reverse proxy.
It removes the option of using uWSGI with Apache
and mod_wsgi.
In the case of Keystone being used in a Federated
Service Provider configuration, it will use Apache
as the web server but for all other environments
it will use Nginx instead.
Change-Id: If6e95fc0d3f7d34780db1aed2b8cedca87499934
84af640aa0