munin: Add plugins to prod hosts.

puppet/zulip_ops/manifests/app_frontend.pp

@@ -68,4 +68,16 @@ class zulip_ops::app_frontend {
     mode   => '0644',
     source => 'puppet:///modules/zulip_ops/cron.d/fetch-contributor-data',
   }
+
+  # Enable some munin plugins
+  $munin_plugins = [
+    'rabbitmq_connections',
+    'rabbitmq_consumers',
+    'rabbitmq_messages',
+    'rabbitmq_messages_unacknowledged',
+    'rabbitmq_messages_uncommitted',
+    'rabbitmq_queue_memory',
+    'zulip_send_receive_timing',
+  ]
+  munin_plugin { $munin_plugins: }
 }