Dataset: Creating a draft dataset from published version fails with some file metadata changes.

[kcondon]

This is seemingly an edge case. Saving each item separately creates the draft without error. Saving them together as indicated fails with stack trace. Steps to reproduce and stack trace follows:

Steps to Reproduce
-Create a dataset and upload a single tabular datafile, preferably 50by1000.dta.
-Publish dataset.
-Navigate to the file landing page for 50by1000
-Click add/edit metadata.
-Select checkbox next to file, choose restricted
-Add a description
-Click edit tags, add all non tab tags, add a custom tag, add all tabular tags
-Save, save changes
-Enter TOA, choose allow request access
-Continue, see error.

Partial Stack trace:
Caused by: javax.persistence.PersistenceException: Exception [EclipseLink-7197] (Eclipse Persistence Services - 2.5.2.v20140319-9ad6abd): org.eclipse.persistence.exceptions.ValidationException
Exception Description: Null or zero primary key encountered in unit of work clone [edu.harvard.iq.dataverse.DataFileTag[ id=null ]], primary key [null]. Set descriptors IdValidation or the "eclipselink.id-validation" property.
at org.eclipse.persistence.internal.jpa.EntityManagerImpl.flush(EntityManagerImpl.java:868)