[FIX] payment: do not refund transactions if they need 3DS validation

This was already the intended behavior, but in Python a return inside
of a try...finally does not behave this way. From the Python
documentation [1]:

When a return, break or continue statement is executed in the try
suite of a try...finally statement, the finally clause is also
executed ‘on the way out.’

This can cause issues because some payment acquirers will return an
error when refunding a pending transaction. This puts the transaction
in the 'error' state which means it won't be refunded anymore.

Additionally, putting s2s_do_transaction in a try...except like this
hides any traceback that occurs which makes troubleshooting harder.

[1] https://docs.python.org/3/reference/compound_stmts.html#finally

addons/payment/models/payment_acquirer.py

@@ -844,16 +844,13 @@ class PaymentToken(models.Model):
             'partner_country_id': self.partner_id.country_id.id,
         })
 
-        try:
-            kwargs.update({'3d_secure': True})
-            tx.s2s_do_transaction(**kwargs)
-            # if 3D secure is called, then we do not refund right now
-            if tx.html_3ds:
-                return tx
-        except:
-            _logger.error('Error while validating a payment method')
-        finally:
+        kwargs.update({'3d_secure': True})
+        tx.s2s_do_transaction(**kwargs)
+
+        # if 3D secure is called, then we do not refund right now
+        if not tx.html_3ds:
             tx.s2s_do_refund()
+
         return tx
 
     @api.multi