Qml: ask old password before changing password

[ecdsa]

in QML, it is possible to change the password without retyping it. if PIN is enabled, the PIN code will be asked.

I think the old password should be asked (whether PIN is active or not), to make sure another user is not inadvertently resetting the password. That was the case in the Kivy app.

[accumulator]

It originally asked for password, until PIN became the default auth_protect method :)