Disable check for existing data after enable constraint checking

Django expect database not to check existing data after enable constraint checking,
This also fixed two errors in backends unit test.

Author: absci

mssql/base.py

@@ -494,7 +494,7 @@ def disable_constraint_checking(self):
 
     def enable_constraint_checking(self):
         if not self.needs_rollback:
-            self.cursor().execute('EXEC sp_msforeachtable "ALTER TABLE ? WITH CHECK CHECK CONSTRAINT ALL"')
+            self.cursor().execute('EXEC sp_msforeachtable "ALTER TABLE ? WITH NOCHECK CHECK CONSTRAINT ALL"')
 
 
 class CursorWrapper(object):

testapp/settings.py

@@ -101,8 +101,6 @@
                   'ordering.tests.OrderingTests.test_deprecated_values_annotate',
                   'queries.test_qs_combinators.QuerySetSetOperationTests.test_limits',
                   'backends.tests.BackendTestCase.test_unicode_password',
-                  'backends.tests.FkConstraintsTests.test_disable_constraint_checks_context_manager',
-                  'backends.tests.FkConstraintsTests.test_disable_constraint_checks_manually',
                   'introspection.tests.IntrospectionTests.test_get_table_description_types',
                   'migrations.test_commands.MigrateTests.test_migrate_syncdb_app_label',
                   'migrations.test_commands.MigrateTests.test_migrate_syncdb_deferred_sql_executed_with_schemaeditor',