Fix Vitrage wrong configuration

* In service_credentials section, project_name should be
admin and auth_url should use keystone public port (5000)
according [1].
* User vitrage should have role admin in project admin [2].

[1] https://github.com/openstack/vitrage/blob/master/devstack/plugin.sh#L164
[2] https://docs.openstack.org/vitrage/latest/install/install-rdo.html#initialize-vitrage

Change-Id: I8bf028c702df5659e4c58df0e17600ab5be14eea