[imp] auto-login to imp w/ Horde 3.0 / IMP 4.0 RC

[liamr at umich.edu]

> It looks like you're getting partial session information, but I really don't
> know where it's coming from, sorry... I'm a bit lost as to how you're
> reproducing this now, also.

Use a transparent authentication driver (such as HTTP).  Log out of 
IMP.  It'll
take you to the Horde portal screen, and you'll already be logged in.  Hit the
back button on your browser.

Chuck - I can probably get you a test account on our server if you'd like to
witness it in person.

Liam