optimize publication status retrieve on documents

In org.nuxeo.ecm.platform.publisher.task.CoreProxyWithWorkflowFactory#isPublished we're scanning for tasks but in the other hand, in org.nuxeo.ecm.platform.publisher.task.CoreProxyWithWorkflowFactory.isPublishedDocWaitingForPublication we're checking for the ACL existence.

We should use the same logic in both methods. It seem that the ACL check is better optimized.

A special thank for Marc Berhaut from AC rennes for reporting this problem.