Avoid using the RoleModel cache because it doesn't yet exist on this bra...

...nch. This fixes a problem in which Garden 2.0 installations will hang indefinitely due to a PHP error when trying to change one's own email address on an account.

Note I am naive when it comes to Vanilla's source code but this seems to do the trick and seems to be the quickest fix for sustaining 2.0 functionality until I can update to 2.1.