Expire packages in "Docker" lifecycle

* avoids accumulation of packages in "READY" state

Author: jochenehret

lib/cloud_controller/diego/docker/staging_completion_handler.rb

@@ -25,6 +25,11 @@ def self.schema
           }
         end
 
+        def staging_complete(payload, with_start=false)
+          super
+          BitsExpiration.new.expire_packages!(build.app)
+        end
+
         private
 
         def handle_missing_droplet!(_payload)

spec/unit/lib/cloud_controller/diego/docker/staging_completion_handler_spec.rb

@@ -48,6 +48,11 @@ module Docker
               subject.staging_complete(payload)
             end
 
+            it 'expires any old packages' do
+              expect_any_instance_of(BitsExpiration).to receive(:expire_packages!)
+              subject.staging_complete(payload)
+            end
+
             context 'when staging result is returned' do
               before do
                 payload[:result][:process_types] = {