Assert db purge cron job

This makes sure the db purge cron job is properly configured in
acceptance tests. The job was enabled in the common manifest a while
ago by the dependent change.

Depends-on: https://review.opendev.org/792743
Change-Id: Ic83d6595cd23319e286719c2e7f766ea1aa3e4da

spec/acceptance/10_basic_glance_spec.rb

@@ -33,5 +33,9 @@ describe 'glance class' do
     describe port(9292) do
       it { is_expected.to be_listening }
     end
+
+    describe cron do
+      it { is_expected.to have_entry('1 0 * * * glance-manage db purge --age_in_days 30 --max_rows 100 >>/var/log/glance/glance-rowsflush.log 2>&1').with_user('glance') }
+    end
   end
 end