[banquepopulaire] rework previous patch, raise BrowserIncorrectPassword only in a specific case

The current source code leads to false positive BrowserIncorrectPassword.
Some accounts got an exception when fetching history or cards coming,
which is correctly handled by the module using ErrorPage.

This patch restricts the BrowserIncorrectPassword 'hack' to the login stage, as
it is the only case we want to catch.