Incompatibility with Login Toboggan and validate email address option when registering new user in slave

There's an incompatibility with Login Toboggan module and Bakery SSO when the "Require e-mail verification when a visitor creates an account" option (also called "Set password" in LT config page).

LT set its own submut hanfler for the register form. In that submit handler the new user is created. After that, Bakery submit handler fires, taking browser to master site, creating site and redirecting again to slave site to the URL where bakery_register_return function is the callback. Then, this function tries to create the user again because of the validate email option so a PDOException is thrown because a duplicate table key error is fired.

I guess Bakery should check if user is already created, but I've not check if this behavior can introduce another bug while fixing present one.

I'll try to check it these days.

Also, looking at the 6.x code I think bug is present too, but I've not tested yet.