Disable caching of tables for migration spec that drops a temporary table

This is to fix job failures, such as https://gitlab.com/gitlab-org/gitlab-ee/-/jobs/51409392.

spec/lib/gitlab/background_migration/populate_untracked_uploads_spec.rb

 require 'spec_helper'
 
-describe Gitlab::BackgroundMigration::PopulateUntrackedUploads, :sidekiq do
+# This migration is using UploadService, which sets uploads.secret that is only
+# added to the DB schema in 20180129193323. Since the test isn't isolated, we
+# just use the latest schema when testing this migration.
+# Ideally, the test should not use factories nor UploadService, and rely on the
+# `table` helper instead.
+describe Gitlab::BackgroundMigration::PopulateUntrackedUploads, :sidekiq, :migration, schema: 20180129193323 do
   include TrackUntrackedUploadsHelpers
 
   subject { described_class.new }

spec/support/db_cleaner.rb

@@ -37,6 +37,10 @@ RSpec.configure do |config|
     DatabaseCleaner.strategy = :deletion, { except: %w[licenses] }
   end
 
+  config.before(:each, :delete_no_cache) do
+    DatabaseCleaner.strategy = :deletion, { cache_tables: false }
+  end
+
   config.before(:each, :migration) do
     DatabaseCleaner.strategy = :deletion, { cache_tables: false }
   end