[1.7.x] Fixed #23089 -- Fixed transaction handling in two management commands.

Previously, when createcachetable and flush operated on non-default
databases, they weren't atomic.

Backport of 753a22a635 from master

tests/cache/tests.py

@@ -989,9 +989,11 @@ class CreateCacheTableForDBCacheTests(TestCase):
             # cache table should be created on 'other'
             # Queries:
             #   1: check table doesn't already exist
-            #   2: create the table
-            #   3: create the index
-            with self.assertNumQueries(3, using='other'):
+            #   2: create savepoint
+            #   3: create the table
+            #   4: create the index
+            #   5: release savepoint
+            with self.assertNumQueries(5, using='other'):
                 management.call_command('createcachetable',
                                         database='other',
                                         verbosity=0, interactive=False)