wallet2: fix background wallet detection in verify_password()

[selsta]

No description provided.

[plowsof]

started wallet-rpc -> setup_background_sync with custom-.. password -> start -> stop (with wrong password) errors -> stop (with correct password) no problems

release 6.6 binary has the same behaviour hm

will try to hit this by opening a background wallet file - as i dont understand when this logic is hit atm

OK:

open a wallet.background as a normal wallet then call "stop_background_sync" - this is ofc not logical as this is a view only wallet already and not background syncing