remove signup links when you can't signup+discussion

Fixed a bug in the process.  In current wagns going to /account/signup when signup isn't supported gives a 500 error.  now it gives a normal denial.

Looks fine. No link on the signin page, or when you try to edit/delete/create something you don't have permission to, and the direct link fails fairly nicely. Closing.

  --John Abbe.....Wed May 20 20:58:41 -0700 2009