[InterNetNews/inn] 002caf: pullnews: Properly exit when a post fails

[Julien ÉLIE]

  Branch: refs/heads/main
  Home:   https://github.com/InterNetNews/inn
  Commit: 002cafdb656d8e7b0f624a7a0b2afc1b35176303
      https://github.com/InterNetNews/inn/commit/002cafdb656d8e7b0f624a7a0b2afc1b35176303
  Author: Julien ÉLIE <Julien-Elie at users.noreply.github.com>
  Date:   2023-02-06 (Mon, 06 Feb 2023)

  Changed paths:
    M frontends/pullnews.in

  Log Message:
  -----------
  pullnews: Properly exit when a post fails

This was already the case when an injection failed (feeder mode).
Do the same when a post fails (in mode reader).

Otherwise, pullnews goes on trying to send articles, and the highest
article number retrieved keeps increasing.  We should bail out as soon
as possible.