postfix-logwatch: NOQUEUE prefix for abnormal connection terminations

postfix-logwatch: NOQUEUE prefix for abnormal connection terminations

In postfix-3.10.0, these lines gained a "NOQUEUE: " prefix:

  https://www.postfix.org/announcements/postfix-3.10.0.html

To support both formats, we strip the prefix early on, and then do
what we used to do. For reference, the full list of reasons can be
found in the postfix source, in src/smtpd/smtpd.c:

   /*
    * Reasons for losing the client.
    */
  #define REASON_TIMEOUT          "timeout"
  #define REASON_LOST_CONNECTION  "lost connection"
  #define REASON_ERROR_LIMIT      "too many errors"