[JDEV] unregister/remove

[David Rosenbloom]

It appears that the jabberd  behavior allows login from users who
have unregistered via a /remove. So that:

- a user registers;
- same user unregisters (/remove with key);
- same user logs in later.

Login is permitted without re-registration.

So my questions are:
- Is this the desired /remove behavior?
- Must the client's datastore be rinsed so that they do not present the
old creds, in order to force re-registration?

thanks,
- davidr