[1.0.X] Fixed insert/update handling when no database interaction is required.

Fixed #10205 as part of this.

Backport of r9926 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.0.X@9927 bcc190cf-cafb-0310-a4f2-bffc1f526a37