SnapshotService - cleanSnaphostHistory

[rsoika]

The method cleanSnaphostHistory uses a JQPL query to test for deprecated snapshots. As the query method runs within a new transaction (new feature since 5.1.9) we can not be sure if the result set is valid within the current transaction. So it might be that the call

 documentService.remove(oldSnapshot)

failed with a EJBException. To avoid this situation (which is rolling back the wole transaction) we need to test if the current document is available. For that we can simply call the load method and see if the document was found in this transaction.

[rsoika]

See also imixs/imixs-workflow#634