Clean up unified limits configuration for nova and glance

This is a followup for change Ifdef3510bc7da3098a71739814e35dbaf612ae34
which added configuration of unified limits for nova. This removes an
unnecessary wrapper unsetting of OS_ env variables, unnecessary quoting
on an iniset config value, and a hardcoding of user domain. The glance
code from which the nova code was originally copied is also cleaned up.

Change-Id: I4921af5cc0f624dd5aa848533f7049ee816be593
diff --git a/lib/glance b/lib/glance
index 9bba938..b94c06d 100644
--- a/lib/glance
+++ b/lib/glance
@@ -309,13 +309,13 @@
     iniset $GLANCE_API_CONF oslo_limit username glance
     iniset $GLANCE_API_CONF oslo_limit auth_type password
     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 system_scope all
     iniset $GLANCE_API_CONF oslo_limit endpoint_id \
            $(openstack --os-cloud devstack-system-admin endpoint list --service glance -f value -c ID)
 
     # Allow the glance service user to read quotas
-    openstack --os-cloud devstack-system-admin role add --user glance --user-domain Default \
-        --system all reader
+    openstack --os-cloud devstack-system-admin role add --user glance \
+        --user-domain $SERVICE_DOMAIN_NAME --system all reader
 }
 
 # configure_glance() - Set config files, create data dirs, etc