[Android] Leaving Ring creation wizard should not be possible without creating an account
Issue generated from Tuleap's migration script. Originally submitted by: Alexandre Lision (alision)
The hardware back button and the arrow in the Action bar allow the user to exit the wizard and use the app without a valid Ring account.
It creates unwanted corner cases and issues, since the user can navigate in the app without any account.
The back arrow should be removed if no other account exists (user may be creating a second account, in this case he is allowed to leave)
The back button should exit the app, not depiling the Fragment.