simultaneously syncing multiple LCEs on smart proxy fails due to "required lock" error
when syncing multiple LCEs simultaneously to a smart proxy, sync tasks after the first will fail due to "required lock" error
to reproduce the issue:
1. publish a new version of a CV, promote it to multiple LCEs
2. if the smart proxy is configured to auto-sync when LCEs are updated, any sync tasks after the first one created will fail due to "required lock"
the proposed solution (thanks jsherrill!) is that the resource locks in `app/lib/actions/katello/capsule_content/sync_capsule.rb` need to be defined as only a 'linking' lock