Use devstack-system-admin for keystone objects creation

This is needed so we can set keystone into enforcing secure RBAC.
This also adjusts lib/glance, which already partially used
devstack-system-admin.

Change-Id: I6df8ad23a3077a8420340167a748ae23ad094962
diff --git a/lib/glance b/lib/glance
index 4c2755f..9bba938 100644
--- a/lib/glance
+++ b/lib/glance
@@ -311,11 +311,11 @@
     iniset $GLANCE_API_CONF oslo_limit auth_url $KEYSTONE_SERVICE_URI
     iniset $GLANCE_API_CONF oslo_limit system_scope "'all'"
     iniset $GLANCE_API_CONF oslo_limit endpoint_id \
-           $(openstack endpoint list --service glance -f value -c ID)
+           $(openstack --os-cloud devstack-system-admin endpoint list --service glance -f value -c ID)
 
     # Allow the glance service user to read quotas
-    openstack role add --user glance --user-domain Default --system all \
-              reader
+    openstack --os-cloud devstack-system-admin role add --user glance --user-domain Default \
+        --system all reader
 }
 
 # configure_glance() - Set config files, create data dirs, etc