[FIX] account: missing parameter in send_mail

d88c34d1 added an auto_commit parameter to send_email of
mail.compose.message but apparently missed updating at least one
override.

Fix that oversight.

addons/account/models/account_invoice.py

@@ -1275,12 +1275,12 @@ class MailComposeMessage(models.Model):
     _inherit = 'mail.compose.message'
 
     @api.multi
-    def send_mail(self):
+    def send_mail(self, auto_commit=False):
         context = self._context
         if context.get('default_model') == 'account.invoice' and \
                 context.get('default_res_id') and context.get('mark_invoice_as_sent'):
             invoice = self.env['account.invoice'].browse(context['default_res_id'])
             invoice = invoice.with_context(mail_post_autofollow=True)
-            invoice.write({'sent': True})
+            invoice.sent = True
             invoice.message_post(body=_("Invoice sent"))
-        return super(MailComposeMessage, self).send_mail()
+        return super(MailComposeMessage, self).send_mail(auto_commit=auto_commit)