Fix two places that can cause issues under SQLite

In both places, we may potentially iterate over a result set after
closing the read transaction.

Change-Id: I0afce854287a4375c525c19c49ed0ec01bac76b1

ironic/db/sqlalchemy/api.py

@@ -387,7 +387,7 @@ def _paginate_query(model, limit=None, marker=None, sort_key=None,
                 return []
             if return_base_tuple:
                 # The caller expects a tuple, lets just give it to them.
-                return res
+                return [tuple(r) for r in res]
             # Everything is a tuple in a resultset from the unified interface
             # but for objects, our model expects just object access,
             # so we extract and return them.
@@ -585,16 +585,9 @@ class Connection(api.Connection):
         # If we are not using sorting, or any other query magic,
         # we could likely just do a query execution and
         # prepare the tuple responses.
-        results = _paginate_query(models.Node, limit, marker,
-                                  sort_key, sort_dir, query,
-                                  return_base_tuple=True)
-        # Need to copy the data to close out the _paginate_query
-        # object.
-        new_result = [tuple([ent for ent in r]) for r in results]
-        # Explicitly free results so we don't hang on to it.
-        del results
-
-        return new_result
+        return _paginate_query(models.Node, limit, marker,
+                               sort_key, sort_dir, query,
+                               return_base_tuple=True)
 
     def get_node_list(self, filters=None, limit=None, marker=None,
                       sort_key=None, sort_dir=None, fields=None):
@@ -1481,7 +1474,8 @@ class Connection(api.Connection):
                 result = session.query(
                     field
                 ).filter(models.Conductor.online.is_(False))
-        return [row[0] for row in result]
+            result = [row[0] for row in result]
+        return result
 
     def get_online_conductors(self):
         with _session_for_read() as session: