Use the recommended default for horizon default dashboards

Let horizon discover the default
dashboards via the INSTALL_APPS (which is already an attribute).
The patch removes the old hardcoded defaults which are no longer
needed nor recommmended.

Change-Id: I3c73756a6d834a9bae69ae6ead235e01cc747593
Closes-Bug: #1455063

spec/horizon_spec.rb

@@ -310,6 +310,11 @@ describe 'openstack-dashboard::horizon' do
           expect(chef_run).to render_file(file.name).with_content(/\s*'help_url': "help_url_value",$/)
         end
 
+        it 'allows HORIZON_CONFIG to use INSTALLED_APPS to determine default dashboards' do
+          expect(chef_run).not_to render_file(file.name).with_content(/\s*'dashboards':/)
+          expect(chef_run).not_to render_file(file.name).with_content(/\s*'default_dashboard':/)
+        end
+
         context 'simple ip management' do
           it 'enables the setting when the attribute is set' do
             node.set['openstack']['dashboard']['simple_ip_management'] = true

templates/default/local_settings.py.erb

@@ -70,8 +70,6 @@ CONSOLE_TYPE = "<%= node["openstack"]["dashboard"]["console_type"] %>"
 
 # Default OpenStack Dashboard configuration.
 HORIZON_CONFIG = {
-    'dashboards': ('project', 'admin', 'settings',),
-    'default_dashboard': 'project',
     'user_home': 'openstack_dashboard.views.get_user_home',
     'ajax_queue_limit': 10,
     'auto_fade_alerts': {