[FIX] fetchmail: do not delete a failing email when using POP

In case of IMAP, the email is simply set as read but in case of POP, the email is deleted. To avoid loosing data (e.g. misconfiguration of server), the email is kept for POP.
Bug lp:1296724, opw 605667

addons/fetchmail/fetchmail.py

@@ -236,12 +236,12 @@ openerp_mailgate: "|/path/to/openerp-mailgate.py --host=localhost -u %(uid)d -p
                                                                  save_original=server.original,
                                                                  strip_attachments=(not server.attach),
                                                                  context=context)
+                            pop_server.dele(num)
                         except Exception:
                             _logger.exception('Failed to process mail from %s server %s.', server.type, server.name)
                             failed += 1
                         if res_id and server.action_id:
                             action_pool.run(cr, uid, [server.action_id.id], {'active_id': res_id, 'active_ids': [res_id], 'active_model': context.get("thread_model", server.object_id.model)})
-                        pop_server.dele(num)
                         cr.commit()
                     _logger.info("Fetched %d email(s) on %s server %s; %d succeeded, %d failed.", numMsgs, server.type, server.name, (numMsgs - failed), failed)
                 except Exception: