If connection is down, make Bunny::Queues#pop return empty responses

To support the same edge case with Bunny::Queue#pop being called
in a tight loop when network connection goes down.

It is better to return something immediately rather than keep
blocking the thread we have no easy way to unblock with the
current "blocking pop" approach that replaces not-entirely-correct
wait/notify implementation.

lib/bunny/queue.rb

@@ -134,7 +134,11 @@ def subscribe_with(consumer, opts = {:block => false})
     end
 
     def pop(opts = {:ack => false}, &block)
-      delivery_info, properties, content = @channel.basic_get(@name, opts)
+      delivery_info, properties, content = if @channel.connection.open?
+                                             @channel.basic_get(@name, opts)
+                                           else
+                                             [nil, nil, nil]
+                                           end
 
       if block
         block.call(delivery_info, properties, content)
@@ -145,7 +149,11 @@ def pop(opts = {:ack => false}, &block)
     alias get pop
 
     def pop_as_hash(opts = {:ack => false}, &block)
-      delivery_info, properties, content = @channel.basic_get(@name, opts)
+      delivery_info, properties, content = if @channel.connection.open?
+                                             @channel.basic_get(@name, opts)
+                                           else
+                                             [nil, nil, nil]
+                                           end
 
       result = {:header => properties, :payload => content, :delivery_details => delivery_info}
 
@@ -208,17 +216,20 @@ def recover_from_network_failure
         @channel.deregister_queue_named(old_name)
       end
 
-      declare!
+      # puts "Recovering queue #{@name}"
       begin
+        declare!
+
         @channel.register_queue(self)
       rescue Exception => e
-        puts "Caught #{e.inspect} while registering #{@name}!"
+        puts "Caught #{e.inspect} while redeclaring and registering #{@name}!"
       end
       recover_bindings
     end
 
     def recover_bindings
       @bindings.each do |b|
+        # puts "Recovering binding #{b.inspect}"
         self.bind(b[:exchange], b)
       end
     end