[imp] autologin creating new sessions mid-session

[Liam Hoekenga]

> It would be extremely helpful if you could narrow down a change that caused
> this. I'm not aware of any big changes in authentication, so I'm a little at 
> a loss for where to start looking.

I'm not sure.  It didn't do this in the beta, and I'm using the same 
configuration on our end.  I've tried switching to the native php session 
handler and that didn't work.  I tried turning off hordeauth passthru 
authentication in imp/config/servers.php, and that didn't work.  In each 
case, every time you switch applications, you get a new sessionID - even 
if you go back to an application you were already using.

Liam