[FIX] l10n_us: ABA/Routing

When defining an ABA routing number with leading zeros (which is
possible), the value will always be displayed without them.

This is because the field is an integer. Since the ABA routing transit
number must be a nine-digit code, we automatically fill it with leading
zeros.

opw-1940138

closes odoo/odoo#31223

addons/l10n_us/models/res_partner_bank.py

@@ -34,5 +34,5 @@ class ResPartnerBank(models.Model):
         result = super(ResPartnerBank, self).read(fields, load=load)
         for record in result:
             if record.get('aba_routing'):
-                record['aba_routing'] = str(record['aba_routing'])
+                record['aba_routing'] = '{0:09d}'.format(record['aba_routing']) if record['aba_routing'] else False
         return result