[rt-users] disable user creation

[Michael Goldman]

I guess I'm just use to the RT 1 way of handleing things, where anybody
would submit a ticket but they wouldn't actually be placed into the
users table. Basically the idea for having a small user table, is so we
can search through it very quickly to add users and remove users as that
becomes required.

We are going to be using this for a ticket program for
postmaster/hostmaster issues where we get around 10,000 e-mails a day
(mostly spam, but none-the-less).

Thank you. 

Michael