* openstack-origin is no longer required when using openstack-origin-git.
* Drop kilo from openstack-origin-git default values because upper
constraints doesn't work in kilo for openstack-dashboard and glance.
* Add flag to allow for disabling upper constraints when using
openstack-origin-git with user-specified git repositories.
Change-Id: I017dfd20e3fe997558c13d15c7d05dd1692e7730