When the app is started, the password is checked against all
wallets in the directory.
If the test passes:
- subsequent wallet creations will use the same password
- subsequent password updates will be performed on all wallets
- wallets that are not storage encrypted will encrypted
on the next password update (even if they are watching-only)
This behaviour is restricted on Android, with a 'single_password' config variable.
Wallet creation without password is disabled if single_password is set
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