[bp] Fix BP recipient

Sometimes when we add a BP recipient, we don't catch the expected
message wich is present on the backtrace: "Le n° de compte que vous avez
saisi appartient à La Banque Postale, veuillez vérifier votre saisie". Because
has-class("app_erreur") have several responses, we prefer the in method.

Closes: 28005@sibi