Switched CORS configuration to use oslo_config
Switched CORS configuration to use oslo_config

When cors middleware was moved into paste.ini, genconfig was not
updated to indicate that the configuration method had changed.
This breaks backwards-compatibility, however since the middleware
supports automatic oslo config detection via pastedeploy, it is
easily corrected.

This patch updates the api-paste.ini file to encourage CORS
middleware to draw its configuration from sahara.conf. It also
moves cors to the beginning of the middleware pipeline.

Change-Id: I4cff577aeff21286d0f9ce13142babec39db5e13

egafford/sahara,tellesnobrega/sahara,openstack/sahara,tellesnobrega/sahara,egafford/sahara,openstack/sahara