Don't attempt to contact registry if it is disabled

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/21679 moved the
deletion of registry tags outside of a transaction, but introduced an
issue where Sidekiq would attempt to contact the container registry
during project destruction even if it were disabled.

Relates to:

* https://gitlab.com/charts/gitlab/issues/1455
* https://gitlab.com/gitlab-org/gitlab-ce/issues/45941

app/services/projects/destroy_service.rb

@@ -173,6 +173,7 @@ module Projects
     end
     def remove_registry_tags
+      return true unless Gitlab.config.registry.enabled
       return false unless remove_legacy_registry_tags
       project.container_repositories.find_each do |container_repository|

changelogs/unreleased/sh-disable-registry-delete.yml

+---
+title: Don't attempt to contact registry if it is disabled
+merge_request: 31553
+author:
+type: fixed

spec/services/projects/destroy_service_spec.rb

@@ -241,6 +241,18 @@ describe Projects::DestroyService do
           expect(destroy_project(project, user)).to be false
         end
       end
+
+      context 'when registry is disabled' do
+        before do
+          stub_container_registry_config(enabled: false)
+        end
+
+        it 'does not attempting to remove any tags' do
+          expect(Projects::ContainerRepository::DestroyService).not_to receive(:new)
+
+          destroy_project(project, user)
+        end
+      end
     end
     context 'when there are tags for legacy root repository' do