Delete legacy rabbit queues

When ManageIQ disconnects from the RabbitMQ service in OpenStack, it leaves
behind the queue(s) used to bind to the messaging exchange for events from Nova,
Glance, Cinder, etc...  The problem with leaving these queues behind is that
without a client to drain the queues, they keep filling up with messages from
the notifications topics of the Nova, Glance, and Cinder exchanges.

This patch will remove any legacy queues before attempting to create any new
queues when ManageIQ connects to a RabbitMQ service in OpenStack.

https://bugzilla.redhat.com/show_bug.cgi?id=1265289

gems/pending/openstack/amqp/openstack_rabbit_event_monitor.rb

@@ -93,6 +93,7 @@ def amqp_event(delivery_info, metadata, payload)
   end
 
   def initialize_queues(channel)
+    remove_legacy_queues
     @queues = {}
     if @options[:topics]
       @options[:topics].each do |exchange, topic|
@@ -103,6 +104,24 @@ def initialize_queues(channel)
     end
   end
 
+  def remove_legacy_queues
+    # Rabbit queues used to be created with incorrect initializing arguments (no
+    # auto_delete and no exclusive).  The significant problem with leaving these
+    # queues around is that they are not deleted when the event monitor
+    # disconnects from Rabbit.  And the queues continue to collect messages with
+    # no client to drain them.
+    channel = connection.create_channel
+    @options[:topics].each do |exchange, topic|
+      queue_name = "miq-#{@client_ip}-#{exchange}"
+      channel.queue_delete(queue_name) if connection.queue_exists?(queue_name)
+    end
+
+    # notifications.* is a poorly named extra-old legacy queue
+    channel.queue_delete("notifications.*") if connection.queue_exists?(queue_name)
+
+    channel.close
+  end
+
   def subscribe_queues
     @queues.each do |exchange, queue|
       queue.subscribe do |delivery_info, metadata, payload|