OSRA273 fix duplicate osra_num on import

OSRA273 fix duplicate osra_num on import
Yes. When the validations are ran, a seq_id is generated based on the persisted records.  If you run another validation, another seq_id is generated based on the "persisted" records and ignoring the non-persisted instances in memory.  Thus, forcing a recalculation by re-nillifying the seq_id prior to save! is exactly what the doctor ordered.  This behaviour also guarantees that if you validate an orphan, then discard it, the seq_id it has been given will be reused by another.