[1.1.X] Fixed #11933 -- Corrected the naming of the cached_db session backend....

[1.1.X] Fixed #11933 -- Corrected the naming of the cached_db session backend. Thanks to mb0@mb0.org for the report and Gabriel Hurley for the patch.

Backport of r13169 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.1.X@13175 bcc190cf-cafb-0310-a4f2-bffc1f526a37