fix(elb): override #all_associations_and_attributes

ListenerDescriptions and BackendServerDescriptions are used to build
ad-hoc collections but are not registered as attributes of the
LoadBalancer model.

lib/fog/aws/models/elb/load_balancer.rb

@@ -223,16 +223,24 @@ module Fog
         end
 
         def reload
-          super
           @instance_health = nil
           @policy_descriptions = nil
-          self
+          super
         end
 
         def destroy
           requires :id
           service.delete_load_balancer(id)
         end
+
+        protected
+
+        def all_associations_and_attributes
+          super.merge(
+            'ListenerDescriptions' => attributes['ListenerDescriptions'],
+            'BackendServerDescriptions' => attributes['BackendServerDescriptions'],
+          )
+        end
       end
     end
   end