Adding support for displaying cluster error details

Required with Cue patch:
https://review.openstack.org/#/c/244308/

Change-Id: I41e8f4e350efed21befdd3864aaff57a777adbd5
closes-bug:  1508730

cuedashboard/templates/messagebroker/_detail_overview.html

@@ -10,6 +10,8 @@
     <dd>{{ cluster.id|default:_("None") }}</dd>
     <dt>{% trans "Status" %}</dt>
     <dd>{{ cluster.status|default:_("-") }}</dd>
+    <dt>{% trans "Error Detail" %}</dt>
+    <dd>{{ cluster.error_detail|default:_("-") }}</dd>
     <dt>{% trans "Network" %}</dt>
     <dd>{{ cluster.network_id|default:_("-") }}</dd>
     <dt>{% trans "Flavor" %}</dt>