Check for any pre-010 provstacks and migrate those to the new slab.

def migrateProvPre010(self, newslab):
        '''
        Check for any pre-010 provstacks and migrate those to the new slab.
        '''
        did_migrate = self._migrate_db_pre010('prov', newslab)
        if not did_migrate:
            return

        self._migrate_db_pre010('provs', newslab)