--auth-password is not supported

[ts678]

@quinting

It seems that if you use Google Password Manager to save your login password for Duplicati, it will automatically enter it in the auth-password field (even though that field doesn’t exist on the screen).

It’s possibly a two-step process, which Firefox “Autofill logins and Passwords” can also do damage on.

1. Password saver may autofill too many places, getting --auth-password is not supported #4102 (anybody out there expert on unconfusing several overly-eager-to-autofill password managers?)

2. Changing backend type leaves invalid backend options #3082
   (which could happen without step 1, and whose fix would prevent step 1 from getting into step 2)