Make ask.openstack.org read-only

Nobody maintains our askbot website, and questions there go
unanswered. In the spirit of simplification, make the site
read-only (so that old answers can still be found) and redirect
users to the openstack-discuss mailing-list and Stack Overflow
(which has a decent openstack community answering questions).

Read-only config values documented at:
https://github.com/ASKBOT/askbot-devel/blob/master/askbot/conf/access_control.py

Change-Id: I33d9d7c87a5a17138fcdc37ee8f8b16cda2248d5

modules/openstack_project/templates/askbot/settings.py.erb

@@ -365,6 +365,14 @@ LIVESETTINGS_OPTIONS = {
     1: {
         'DB': True,
         'SETTINGS': {
+            'ACCESS_CONTROL': {
+                'READ_ONLY_MODE_ENABLED': True,
+                'READ_ONLY_MESSAGE':
+                    'The ask.openstack.org website will be read-only from '
+                    'now on. Please ask questions on the openstack-discuss '
+                    'mailing-list or on stackoverflow.com instead (use the '
+                    '"openstack" tag).'
+            },
             'GENERAL_SKIN_SETTINGS': {
                 <% if @custom_theme_enabled %>
                 'ASKBOT_DEFAULT_SKIN': '<%= @custom_theme_name %>',