Check account vs db id during unlock

[matheusd]

When using the remotedcrwallet driver, during the driver initialization it ensures the account being used is the same one as the previously used ones (specifically, here).

This check could (also) be done during the wallet unlock call of the WalletUnlocker service so that an error is synchronously returned to callers instead of waiting for the driver to start the init phanse and casuse the dcrlnd process to exit.

This would improve the UX in decrediton where we could capture this error more easily and present a better message than just time out connecting to dcrlnd