Fixed #21239 -- Maintained atomicity when closing the connection.

Refs #15802 -- Reverted #7c657b24 as BaseDatabaseWrapper.close() now
has a proper "finally" clause that may need to preserve self.connection.

django/db/transaction.py

@@ -205,7 +205,12 @@ class Atomic(object):
             connection.in_atomic_block = False
 
         try:
-            if exc_type is None and not connection.needs_rollback:
+            if connection.closed_in_transaction:
+                # The database will perform a rollback by itself.
+                # Wait until we exit the outermost block.
+                pass
+
+            elif exc_type is None and not connection.needs_rollback:
                 if connection.in_atomic_block:
                     # Release savepoint if there is one
                     if sid is not None:
@@ -245,13 +250,18 @@ class Atomic(object):
         finally:
             # Outermost block exit when autocommit was enabled.
             if not connection.in_atomic_block:
-                if connection.features.autocommits_when_autocommit_is_off:
+                if connection.closed_in_transaction:
+                    connection.connection = None
+                elif connection.features.autocommits_when_autocommit_is_off:
                     connection.autocommit = True
                 else:
                     connection.set_autocommit(True)
             # Outermost block exit when autocommit was disabled.
             elif not connection.savepoint_ids and not connection.commit_on_exit:
-                connection.in_atomic_block = False
+                if connection.closed_in_transaction:
+                    connection.connection = None
+                else:
+                    connection.in_atomic_block = False
 
     def __call__(self, func):
         @wraps(func, assigned=available_attrs(func))