/sbin/e-smith/signal-event ibay-modify <ibayname> should do the trick.
However you shouldn't need to do this when adding a user in Server Manager. I haven't had any issue with this. Which beta of SME 7 are you using?
If it's beta 8, you should search in Bugzilla for a bug about this, and add one if it isn't there already.
If it isn't you should upgrade, and see if it is still happening. Good Luck!
RonM