Fixed #16533 -- Stopped the memcache cache backend from raising an exception...

Fixed #16533 -- Stopped the memcache cache backend from raising an exception if the timeout value isn't an integer. Thanks, Jeff Balogh.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@16556 bcc190cf-cafb-0310-a4f2-bffc1f526a37